because it sure doesn't seem like it.

PA decided the way mount XP with event used to be calculated was an error. Instead of multiplicative function, it now uses additive function. Thus, the event boost lost much of its value. It used to double your XP, now it just adds +100% to whatever you had, so if you already had +400%, you now have +500%. Before, it was 400% x 2. Abandon all hope, I tell you.

I figured that's how it worked all along since I started.  When was it that it was multiplicative?

It was changed to additive just several patches ago - when the buff UI was released. PA realized that all lifeskill event XP buffs are additive and training was not. So they decided the clever thing would be to nuke training XP events by aligning how it works for all of them. There is a long thread somewhere where a guy tested the precise numbers, showing that training events are essentially non-consequential now, since they are not much different from normal training...

Too bad, my desire to train horses during the events died, because it got comparably really slow. I do not need anything from training and it seems like a too much of a waste of time now. Better be fishin', mon. Glad I did the sanctuary and all before this mindless nuking.

Thanks for letting us know.  I've dropped training for fishing, too.  PA really knows hows to ruin a good thing when it comes lifeskills.   I used to gather truffles before they let you produce them while afk with alchemy. 

I don't understand why the total amount of Mount Exp isn't shown in that buff UI thing....IT'S THE ONLY ONE!!!