Personally, I think that the ''inbetween'' position switches have become more unpredictable in the last 2-3 seasons, but take this with a grain of salt.
Yeah in the past 2-3 seasons, but like you say "with a grain of salt", I may just be wrong or misremembering.
The guy I started at SG has 9 stamina, and he actually got substituted for 3 minutes while the starting PG with much lower stamina played the entire first 3 quarters.
I've also had difficulty (in the past 2-3 seasons) using a player as substitute for both PG and SF positions, but I can use the same player to backup the PG/SG positions, the SF/PF positions, and PF/C positions. The same thing happens as in the previous example, he will sub in for the SF, but even though he has plenty of stamina I don't think he substitutes for the PG, at least not until the PG simply can't play anymore.