I don't know, never played with that mod. But going by logic alone, that's exactly the kind of mod where I would expect to see such a change, because it's a mod that mostly adds stuff towards the end. The author might have run into the overflow issue and come to the conclusion that changing the game speed scaling is the the cleanest way (that I can think of) to prevent people from running into the issue without having to make changes to the techs, buildings etc. from the previous eras.
That's pure speculation of course, maybe he just thought that players would not want to play with 300% modifiers if there's additional content towards the end.
But in either case, changing the game speed modifiers circumvents most compatibility issues with other mods that would arise if the author were to make changes to other aspects of the game, because the game scales everything automatically. Unless the authors of other mods have used some fixed turn intervals per game speed in their code instead of basing them on the game speed modifiers, most mods should not run into any compatibility issues.
Of course in a project such as this, compatibility with other mods is, let's say, at best a minor concern, so other solutions may lead to more fitting results.