Absolutely. Unfortunately, I found myself in a situation where I added a couple of complementary pieces to the roster who came in with 8+ stamina, and it took a couple of to drop enough that they would occasionally be substituted even in a Princeton. I suppose compared to the issues with people having trouble getting guys 48 minutes, and compared to some of the other issues related to the substitution patterns, it's really a small thing.
I've got the opposite situation. To play fcp I've had to add stamina, which has now led to a situation where I have mostly 8 or 9, and some new additions with more normal levels (4-6). One thing I've been able to do is have one player backup two starters because the different stamina levels of the starters means they're actually substituted at different times. I'm not 100% convinced I can do this all the time but its something worth noting.
I kind of thing it would be a neat idea to have stamina training work so that you can set a target stamina value (say, 6) and then when you train, anyone who is over that tracks down toward it and maybe that helps boost anyone below it to get there faster. There's significant balance issues (pick up a whole slew of 9 ST scrubs from the TL, set your target at 8 and you've massively upgraded your real players quickly), so I don't think it'd be a serious proposal, but it's a fun thought. I just hate the notion that something that supposedly is there to make your players better (and it does, generally do that) is still something that doesn't make sense if you believe in getting any sort of rotation in your players' minutes.