Those aspects create imbalances, yeah, and as a result they can be used to balance characters in various ways.
Want a glass canon who has amazing offense, and bad defense? then nerf his defensive options, not his recovery, and then give him good offense. if he has bad rolls, tech rolls, spot dodges, and shields, even if his recovery is okay, getting hit will still leave him in bad situations on a regular basis.
it's a type of balancing tool.
like how in traditional fighters, characters with an abundance of multihit moves suffer from damage scaling more than characters who have many single hit moves. or how some characters have low HP to offset their high offensive capabilities vs characters who have high HP to offset their huge size/huge hurtboxes and inherent weakness to instant overheads.
Can be used to balance characters, but there is no logic to most things that are different.
-is there logic that Zelda standing grab was like 12 frames in melee, it's not like her grabs are OMG SO GOOD.
-Was there logic to ness and Lucas having 40 frame grab-releases, marth having 25, and bowser Dk having 20?
-Why was G&W shield horrible in melee, was he seen as too f'n good.
-Your explaination to peach air-dodge makes some sense but thats the answer to balancing her floating? How about making her aerials not as ridiculous, oh wait brawl did that and gave her a ****ty air-dodge, and look what happened to her.
-Is there a reason Jigglypuff shield kills her, was she seen as a god send in 64 that she needed to be capital punished for blocking?
-Samus's rolls were bad because...........
-Falcon's tech in melee was used to balance him right? right? I don't think so.
-Again Falco, Link, DDD spot dodges were god-sends in Brawl for what reason again?
-Why is Samus tether grapple so much worse then Links even though they are the same function?
and so on...
As you can see there is absolutly no logic to ANY of these arbitrary differences, to say they were intentionally designed those ways to balance the roster is not true.
These changes do the exact opposite of balance they create horrendous imbalances among the cast.
If they are to be different there needs to be reason to it, and a very clear reason to it. Something like "these characters are light, therefore they ALL have faster rolls to help them evade damage better."
Sorry for the late response btw.
EDIT: you also just said the reason RE grabs were made universal was because only a few characters could do it. See even you guys saw the IMBALANCE that created when they weren't universal.