There kind of been a pattern where Oda hands W to admirals after giving them a L since Wano
After wi fi diff, we got Ryokugyu folding Weevil (most hyped warlord after Mihawk) and mini flashback of Kuzan negging half of BB's crew + making him nervous despite being alone
After Pizzaru, we got Issho's supreme grade, food diff SBS and Akainu's 5B bounty.
If Silver Axe is really an undercover marine that was (or became after GV) an admiral, I could see him get a nice W after Xebec killing the nameless admiral.
One issue is I have with the theory is that it didn't seem like Sengoku was talking of Silver Axe as a fellow marine, he namedropepd him alongside pirates like Shiki & co. But this is just me focusing on one line (and it's not like Sengoku actually called Silver Axe a pirate) and Oda did much worse retcons .