No, a 12.5mm drop – those are diameters. But yes, less with a bigger volume tyre.
Yes, sorry, my mistake; a 25mm difference in diameter, so 12.5mm BB drop.
Not quite the same, but I’ve been playing with B+ wheels in my 29ers which drops the BB by ~7mm.
On the Solaris it’s been great. The BB was probably a bit high (with a 120mm fork) so the smaller wheels let me keep the travel and angles I like while lowering the bike a bit (plus a bit more comfort and grip from the bigger tyres).
By contrast it doesn’t really work for me on the Smuggler. The BB was already low and gets too low for my liking. Being a full suss I don’t get as much benefit from the extra cushioning of the bigger tyres and the heavier wheels make the steering (on what is a pretty slack bike) too sluggish.
So, yes, it does seem to very much depend on the bike and on you of course.