The thing is, gamewatch's interview said it was an ability to let the next one hit 3 times but
then corrected it.
I believe this was corrected in the original Japanese as well.
It was corrected to say we're getting an new weaponskill that hits 3 times.
Famitsu's says
A bit more ambiguous but still more fitting to the correction.
Both those articles contradict one another about Issou (Famitsu says it buffs a single weaponskill, Gamewatch describes it more as a buff with a duration) so it's all taken with a grain of salt.
But at least they don't contradict one another for Mugen Sandan, so I'm inclined to believe Gamewatch wouldn't have corrected it just for it to turn out to be the original.
Unless you have a interview source that still directly contradicts this.
So I can fully trash all their information.