No it's oda trying to fool his audience and pretending he was already strong just never did anything to show it...
He wont ever become physically strong. My money is on Tilestone (who?!) vs Usopp every day of the week.
However, Izo was a 500M bounty and he didnt strike me as a particularly strong guy either. Even Marco isnt all that in strength.
What Usopp could develop is a CoO approaching Fujitoras, that was seriously impressive in Dressrosa vs Sugar. And he could replace those toys he uses with, I dont know, GUNS. Same as Izo, Kaido, Doflamingo, Yasopp.
Adding that could propel him to the level of Izo, someone he has history with and should use as a role model.
Usopp already has top tier aim so secondly he needs to learn to imbed the bullets with haki. This is the fault of Luffy & Zoro. Both are adept at CoA, Zoro even with a weapon/object, but neither has taught the crew anything. Send Usopp to Amazon Lily for 2 months to learn to imbue projectiles with haki.