That doesn't factor in a 1v1 and zoro saving luffy doesn't ascend his tier above his captain.. logically luffy knows in hindsight that if he goes all out and runs out of gas.. zoro is there to carry him until he regains his haki.. unless you think he never expected zoro to save him as a crew member. Sanji or Jimbe logically would do the same thing..
that doesn't mean they top their captain coz of that
Ist In a 1v1 he wouldn't have gotten past the ragnorok, or had no defensive ability after his haki was drained from g4 that very much factors in a 1v1 seeing he did the same thing against both cracker and katakuri, he just had nami and Brule to help or hold hostage respectively and let him recharge his haki.
2nd i agree, zoro saving luffy does not mean he is a higher tier, nojiki and pinwheel guy saved him before also
But being able to jump up in front of and deflect (momentarily) an attack that luffy saw with future sight when no one else could (including luffy) and
scarring someone who as luffy even stated he's trying to penetrate his scales (only one person on the roof had penetrated the scales and he did it twice) but I would at least think you would realize Zoro is the only person we've seen or heard of overpowering (kaidos words) an attack with his own attack, luffy hasn't produced an attack that can nullify one of kaidos (named) attacks and deal damage which should tell you there's a difference in stregnth