Why so triggered bro, we are just talking on a forum, calm down.
For your information, I started out with boxing/kickboxing, then went on, after 3 years, to bjj, which since has became my main focus (I also compete on a regular basis) but I still attend 2-3 striking classes a week as a hobbyist.
So I'm not an expert striker, but have I ever pretended to be one? No, I'm just giving my opinion and trying to friendly debate, so stop hating...
Whatsoever, yes I think if striker A (the boxer) has as much grappling experience as striker B (the mt guy), there are as much chances (at least) that striker A wins, since everything he's throwing won't put him of balance, and that he knows how to defend punches.
Moreover, let's not forget that there is no possible comparison between a mt guy's punches and a boxer's ones...
Of course, striker B would have his weapons too, but stop acting like striker A wouldn't stand any chances...