The reverse summoning also makes sense, because we've seen that whenever a summon gets too weak it gets reverse summoned back. Also, Susuke didn't expect Manda's consensus when he summoned him- that's why he trapped Manda under a genjutsu and basically used him as both a meat shield and a transporter.
However, a potential plot hole can be argued if you think Manda died during the blast itself, because Manda would have disappeared from the snake register and should have become unsummonable, like
what happened to that one frog Danzo killed.
Also, we don't actually know whether Manda/summons get reverse summoned when they go back rather than just getting sent back some other way, since the summoner would need to be aware that the summoned was weak.