The "small part" is not that small at all from what I know, and I think they overdo the testing a bit, especially when I tell them the games have been on the market for months and therefore already thoroughly tested by the players, but it's their call...
Being a regular consumer of BFG titles and having beta tested more than a few of them, I can tell you that all that testing is indeed needed. For every great game put out by Elephant, ERS, or BoomZap there are a dozen others that look like they just ran their original dialog through Google translate to get it into English (one was so bad... I mean, "All your base are belong to us" bad...).
Even being released into the wild isn't enough. I'd be willing to bet that the customers who shop at Amaranth or similar portals directly are a lot more 'forgiving' when it comes to their RPG's than BF customers are. Yeah, you've got those reviewers who 5 star every game that comes out (or so it seems), but then come all the real reviews - and I've got to give Big Fish a lot of credit for this: they post them all - the good, the bad, and the ugly. That's why I shop with them instead of any of the other similar sites - Viva used to have reviews, but strangely enough, none were less than three stars >.> Now they don't post reviews at all.
Anyway my point is that even if the game is 'good enough' for the smaller RM market, if it isn't up to BFG standards it will be (rightly) blasted in the reviews and forums. Too many of those, and it starts to reflect on BFG, and naturally that's a situation they would rather avoid. It will be interesting to see how that dynamic pans out on Steam over the long run, after a more than a few games get up there and people post what they really think.
Another 'logistical' problem with BFG is game length. They like games in the four to six hour range. Four to five hours and you've just finished the "demo" part of my project if you bothered to talk to people and follow the story. They even broke Syberia up into three parts to make it fit that paradigm, leaving a lot on the cutting room floor from what I read
Btw, the original Syberia is still out there and I HIGHLY recommend the game - GameRoomsWithStyle is a 3rd party seller I bought my copy from. There was a problem the idiots who wrote the launcher caused (the game launched into Lost Lagoon 2, with no Syberia option). I finally got it figured out and emailed them what happened and what to tell their customers to fix it, and they really took care of me for it. They don't have a lot of sales yet, but they look like a couple guys trying to start up and earn a honest living. I'd pay an extra couple bucks to buy from them again. (I have no relationship with the company other than buying that title and receiving awesome, personal customer service)