DraQ
Arcane
Personally my favourite among party based RPGs in regards to party size would be Wizardry 8 - core party of 6 with additional 2 slots for recruitable characters bringing total party size up to 8.Touche. "The traditional party size of 6" can only be traditional if you only played games with 6 party members, but this is not the case for many games labeled as RPGs:
Neverwinter Nights 1 - a party of 2.
Neverwinter Nights 2 - a party of 5.
Knights of the Old Republic 1 and 2 - a party of 3.
Planescape: Torment - a party of 5.
Dragon Age: Origins - a party of 4.
Mass Effect 1 & 2 - a party of 3.
Pillars of Eternity 2: Deadfire - a party of 5.
Fallout - no "traditional limit" as such. You can have as many as you want (you have a total of 4 permanent companions, giving you a party of 5).
Arcanum - no "traditional limit" as such (you can a party of 8 going, if you know how. Maximizing charisma alone will get your party to 6).
Fallout 2 - no "traditional limit" as such (you can get a party of 6, if you max your charisma to 10).
Wasteland 2 = a party of 7.
Disclaimer: all parties include the main character as part of their party.
And there are many other games (including old games), which have party limit other than 6. Just look at Ravenloft: Strahd's Possession. The game from 1994 has a party limit of 4. So how is this in any way shocking that we're getting RPGs where party limit is 4, instead of 6?
Also PS:T had party of 6, not 5.