I haven’t played the newer version but I’ve never managed to win and kill all the monsters and get more than 1 block.
But I did manage to win last time by destroying 3 blocks but getting 13 health anyway. Because lately instead of taking wild guesses if I don’t have enough health to use it all up and still be completely safe, I’ve been using the walls to soak up the extra HP instead. It generally is just to keep myself safe and recoup 1 or 2 xp, because usually by the time the wall has soaked up 3 hits, I’ve moved well past the wall and so the revealed tile won’t give me any new information. Sometimes it does, though.