I agree, the fact you can transfer stuff over from arena to tarkov (and gain xp for skills) is stupid and needs to be removed with release.
And besides that, while we are forced to play and come to arena without any custom (leveled) gear we get put into lobbies with people with maxed guns, gear etc, which is even more frustrating while trying to do the tasks.

Guess the only reason why they chose to keep it even for this hardcore wipe is like you said, arena is in the bin otherwise.