I just changed the almost-new (518 miles) '22 SV+ Leaf fluid out, and it is kinda surprising. Gears like this don't typically get the surface roughness already polished down completely at the parts factory. It "wears in", while in service, and we hope the magnets catch most of it. .... I ran across an Eaton co. patent the other day ( https://patents.google.com/patent/DE60130835T2/en
) which said the Ra (RMS peaks/valleys asperities roughness) should be between about 3 microinches to 10, ideally.
I can't figure out why Kia/Hyundai doesn't put in factory-installed magnets either. It does seem to help a lot. Cascading wear due to loose iron particles just keep grinding down the gear teeth & bearings. Tesla puts a magnet & even an oil filter on many of their later models to really get the most life and also to prevent warranty claims.
I put in Valvoline Maxlife ATF (kv100 5.9 cSt) for now, and will change it again a few months from now for it's final fill of Redline (mostly PAO/POE) MT-LV 70W GL-4 which includes a lot of phosphorus anti-wear chemicals in a proven formula for non-hypoid racing & street gear sets such as manual transmissions, DCT's, AMT's, transfer cases, etc.