I'm not surprised considering that you don't understand what "Completion Time" means.
The information was clearly displayed in one tutorial popup but I did not think to screenshot it for retards like you.
Anyway, first google result:
https://www.reddit.com/r/MonsterHun...a_stop_attacking_the_monster_when_someone_is/
To begin with, you're linking to Reddit as a source, which is hilarious in and of itself. Regardless, as
Shackleton pointed out, that thread has 0 upvotes, and the top-voted comment clearly states that the OP is wrong—or at the very least, that it's an unpopular opinion. In other words, you just played yourself, and in a particularly ironic way since you've been screeching about my failure to read some tutorial pop-up.
Lazing Dirk and I have co-oped the entire game, and we know from experience and beyond all doubt that there is absolutely no issue with attacking a monster while the other player is mounted. There can be exceptions, such as if you're using a paralysis weapon, but other than that, it's almost purely beneficial to attack during the (very lengthy) mounting sequences.
If there is a tutorial pop-up that I missed or forgot, then it's flat-out wrong.
I've checked the game tutorials and it's not there therefore I was wrong about the tutorial popup. My bad.
On the other hand, not hitting the mounted monster is the correct strategy: once the mounter executes the charged hit then everybody from the team can hit the monster weakest points. There are like 3-4 mounts per fight because the chance of success diminishes with each mount and players should use that period of time to sharp, buff or whatever. The damage at the end of a successful mount outclasses the damage during the mount because in the end all 4 players are able to do max damage to the monster.
I use the Greatsword and I'm doing regularly something like 200 damage on the mounted monster and 80 + 150 + 400 on the downed monster. There is no way I can do that damage when the monster is running around ... with one exception: sliding-jump damage (but you cannot do that in some places). Basically if you hit the mounted monster then you fuck me as a Greatsword user because the only option remaining is to run around the monster and hit the tail, head and front-arms (but only once because tempered monsters will fuck you up if you try to do two hits in a row).
There is one strategy which works best with mounted monsters: flashbomb them but besides of this hitting the mounted monster is a waste of an opportunity.
Do you get my point?
So I went and did some testing, since this shit is super easy to test. Results:
Monster downtime is about ~9 seconds, depending on when you want to start counting. I spam opened the map to check the time asap after the monster went down, and hit the button to open it again when I heard their feet thump on the ground when they got up for a consistent measurement. Time was consistent across various monsters, from low rank pukei and tobi to HR odoggo and fiery jay leno. Jay leno seemed to take slightly longer (less than a second) which I think can be chalked up to a longer standing animation. Downtime didn't vary whether the monster got finished by my fancy lance stab or a dagger to the head or smashing itself onto the wall. It also didn't matter whether the monster was berserk or exhausted.
Actually downing the monster varied quite a bit- getting the special attack off was easiet from the first mount, it'd trigger before the minimap circle even stopped being all foggy and it'd knock the monster down. I had 2 mounts where the monster let me keep stabbing after my finisher; in both cases these were my third mount, and I don't think I'd gotten the finisher in the second mount. The first time I got a second finisher off, the second time it fell over after some more dagger stabs. Also, it tries to shake you off way more while berserk. Since I'm assuming that raises it's exhaustion (like the real thing, not just to down it), mounting while it's berserk is probably the way to go.
Position on the monster seems to determine how fast you can stab it. Sitting in the middle of a monster's back seemed to consistently let me get those precious 1's faster while the head was a lot slower. Might be a good plan to sit on the back while stabbing and move to the head/tail for the finisher.
I also tried a mount where I just didn't trigger my finisher when it let me. Monster sat there for AGES waiting for me before it finally cancelled out of it and resumed staggering around. Seemed pretty exhausted at that point, didn't try to shake me off much. I ran out of stamina after a while of not attacking, mostly from jumping around too much. Could probably abuse this to give everyone a chance for extra buffs or something on a nasty enough monster that you needed a breather like that.
TLDR: Just hit the monster while it's mounted if you're already healed and sharpened, it'll only be downed for ~10 seconds anyways and the finisher doesn't matter.