SPG-9 shouldn't be able to destroy caches

So i was playing on Kokan with my squad and operating the SPG.
I saw 1 US Inf moving in onto the cache and thought it would be a great idea to throw a Frag round at him.
I fired, hit the wall, the dude flew away and for some reason the cache decided to blow up.

He was outside the building, i hit the outside wall and the cache inside blows up..?
You need up to 7-8 direct RPG-7 hits to blow the cache up but the detonation from 1 single SPG-9 Frag round 15m away from the cache is enough to take it out?
I belive this didn't use to be the case before 1.0 so someone tweaked the SPG-9.

So my question
1. Why?
2. Can you please defuse the SPG?

I almost got banned because of this bs and i don't wanna know how many newbies got banned because they accidently took out a cache.