The main reason so many umpires think trying to change more than 1 batter at a time is a projected substitution is because NFHS actually used to have that as the definition of a projected substitution. They did finally change is several years back, but even then they had 2 conflicting posts on their website, one said changing more than one batter at a time was a projected sub and the other said it was not. Unfortunately the incorrect post saying it was a projected sub came out first and got sent out and was posted on a lot of state softball websites. About 2 weeks later they came out with the second statement that apparently did not get sent out to all the states and so the incorrect ruling remained posted for years. NFHS did finally remove the incorrect ruling but the damage was done.I got this confirmed tonight because I was 95% certain, but then did a google thing and saw different/incorrect information so I paused and deleted my original post.
The number of umpires who don't actually understand "projected substitution" means is staggering. Can't tell you how many times I've had umpires tell me I can't, for example, sub for the first three hitters of the inning all at once before the inning starts. It's frustrating, but I don't actually argue it because it doesn't affect the game.
I would be surprised if an umpire allowed an actual projected substitution with how many won't allow a regular substitution because they think it's a projected substitution.