It technically still “roughly” in case of “extra time per word”, but it is exact for other timer. Because words have different sizes it’s closer to “extra time per average word”, for example it will not spend as much time on word “I” but spend longer on very long words. After testing I found that to be much more accurately match the reading speed after adjusting without the need to manually advance because it takes too long or rollback because I couldn’t read it fast enough. But it generally pretty accurately represents how long it will take for average sentences per word.
You did great, my guy. It is by far the best settings menu I've ever seen in one of these VNs, for so, so many reasons. Unlike just about every other VN I've ever played, I was actually able to configure literally everything I wanted perfectly. Auto is actually usable, volume is configured just to my liking, transition died too, it's great. Though I do wish "Global Transitions" would have some kind of tooltip on Android (dunno if it does on PC?) because it's pretty unclear what that actually does.