I'll hop into Isabelle forums at some point and try and get this figured out but note that your spreadsheet is using DISTANCE as a measurement threshold when i'm hypothesizing that it is FRAMES OUT that increases damage. Those are linked but don't necessarily correlate because a smash fishing rod toss reaches farther faster than a still one. And grounded vs. aerial grab/throw may differ too. If someone jumps into a fully extended rod and gets grabbed on the retraction, it does more than a regular full-distance grab.
When standing still, doing a fresh, grounded, unstaled grab on ZSS, then doing a smash fthrow, the difference is -0.7% between patches. Isa's sideB does more damage as the buoy is extended longer (frame-wise) but the difference is always 0.7% between old patch and this patch from what I can see. Regardless of whether we feel comfortable posting that number, though, we all agree it's different