At the networking stack level, it depends on how one implements congestion control. AFAIR, in the case of Apple/MPTCP: they were sending the same packet on both

At the networking stack level, it depends on how one implements congestion control. AFAIR, in the case of Apple/MPTCP: they were sending the same packet on both the interfaces and hoping for the best delay (a really bad idea) unless you are in a managed network else you are just creating unnecessary congestion. OTOH, if the last mile is oversubscribed, there is very little one can do.