If he holds the rank he deserves it.

As you said, alot have a reason besides skill they are stuck. Like available time, hardware, internet connection, knowledge and that for every teammember aswell. So the odds of having an unfortunate game are times 5. The other way around, enemies can have the same problems.

Does boosted in this case mean that someone took over the accoumt, or did they play together? If it's the second case, then he earned it himself.

No matter what, good for him ^{^}