Claiming it has nothing to do with power level is completely false.
1) That is a good feat from Chopper which hypes up his guard point to be able to take no damage from a Big Mom slap
2) Robin failed which shows her limitations
3) Sanji failed. Without Law's help he would've been defeated and the crew would've been attacked. This showed Sanji's limitations...he was a low diff for DD. If he was stronger, he would've been able to hold his own.
4) Nami was being protected by King Baum and the trees so that doesn't really say much. However, that fight showed Nami's stamina being able to constantly wet biscuits for 11 hours.
5) And Zoro made it his mission to be strong enough to protect his Captain because he believes his dream will be meaningless otherwise.
Crybaby Chopper who cried when he lost to Pero put himself in danger when he saw Nami in danger.
Point is, the strawhat are willing to put themselves at risk to protect one another when danger arises. Because Nami would had been seriously wounded if not for Chopper.
Seeing how Robin didn't confront Kizaru but only wanted to move Zoro away from him show it not a power level discussion.
Now when Sanji failed? What did he say to Nami and Chopper when they about to attack Doffy?
Sanji said Run...
So unless you saying Nami and Chopper can do something against Doffy, it not about PL but them wanting to save Sanji.
Nami also blackmailed those homies, so has everything to do with to support Luffy against Cracker.
Where was that stated by Zoro?
Zoro when he begged Hawkeye is because he wanted to be stronger in those 2 years. Also not only Zoro but all the strawhats wanted to be stronger for Luffy.
Now another example of the strawhats protecting one another is when Kuzan wanted to smash frozen up Robin but Usopp dash to save her from him.