Wow, this is a can of worms...but I'd like to try and post on the topic...
For me, when dealing with old pouches especially, the more of them I see, the more I find making any but the most basic generalizations about them collectively is increasingly difficult, there is just so much variety...as soon as you say they never did it like that...here comes an example where someone did...but then you still have to guess who made it, where and when.
About old pouches being lined...I have seen and repaired "one"...so was lining a pouch fully a rare thing for an old bag maker to do, based on the number of unlined ones Ive seen, yes, I think it was a rare practise...
Today lined bags are definitely much more common...but aren't they equally valid as examples of artifacts from the over all culture of the long rifle...only modern?
I'm not implying that we should ever forget or stop or our continued research to try and understand how and why things were done in the past, to me that is very important...but I think the time is also right for us to ask and document the same about how and why things like lining bags are being done right now, rather than to simply debate if its right or wrong to line them.
Calling this a hobby almost implies that it is like a game with a strict set of rules...and sure, in some juried or even individual cases that is indeed the way it is, but in general I like to advocate tolerance for some evolution and especially artistic licence especially when its identified as such.
That said, I use alot of full welts and rarely ever line the bags I make..
tc