This isn't a glitch. Attack styles are now tied to weapon type, rather than saved as the last one you used.
To safely ensure you don't gain XP in unwanted styles, equip one of each weapon (or at least the weapons you plan on frequently using) and set the intended style on each. This should remove any worry you experience, and will also retain the intended style across weapon swaps.
Yes, in the initial launch of this change, there was a bug that meant some people gained unwanted XP as a result of said bug and not their own fault, but those cases were all handled and fixed back in April.
You have had more than ample time to become acquainted with this change in attack styles, and sadly, while it is definitely a pain to have to remember this and change settings on multiple accounts, to claim that Jagex gave no indication of this happening is quite simply not true.
While I understand your frustration, this is just how the game works now after the update, and sadly there's nothing that can be done to reset your stats due to XP gained because of this change.Community Manager for Jagex