Yes but that is not linked to durability, its, inuniverse, acknowledged as will power
In east blue, when Zoro gets his innards blown out by Mihawk, he didnt die and not because he has his defense level point leveled up but because of willpower, even the manga states so. He is not more durable than a normal human, thats why Hawkins spits nails on him he bleeds from them 900 chapters later

This was always the case, your durability without usage of any power doesnt level up in One Piece. Thats why if any character has above normal naturally durability it mentioned, like big mom.
Bruh Pell survived a nuke

gedatsu survived falling off a sky island

One piece characters in general are superhuman
 
All this is based on the hypothetical that Shamrock is the main antagonist of Elbaf

We have no idea if he's coming back. And if he does, who's to say he won't bring back his daddy?
Oda made Luffy talk about finding the whereabouts of Shanks multiple times this arc. Shamrock is Shanks brother and has the same face as him.
Loki is the obvious Yamato/Oden/Momo of this arc and a clear ally.
Gaban debunked Shiki main antagonist and is a obvious ally as well.
Now Gunko got matched up with Nami/Brook/Ussopp/Jinbei/Colon.
Giants/Gaban might be fighting another.
So clearly none of these gods knights on the island are a Luffy fight. Which obviously means that Shamrock is coming back. Who's to say he would?
 
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