and if some app doesn't really need any frameworks that are only available on Catalina and Big Sur, it shouldn't try to make users upgrade to Catalina and Big Sur to use it. Many Mac users will probably stay on Mojave or High Sierra for a while because of the 32-bit support (there might not be many apps that are 32-bit only and didn't get an update to 64-bit that many users need, but if someone really needs some app and it doesn't have a 64-bit version, one such app could be enough to make someone stay on Mojave, until someone can find a suitable replacement for it).

and if they only have one Mac that is running Catalina to test the app on, instead of deciding to just require Catalina, they could have just installed an earlier version on a different partition or at least in a VM if that Mac was too new to support installing a version before Catalina on another partition. it seems kind of preposterous when some app that doesn't really seem to need some Catalina specific frameworks like CoreM元 or something similar is just requiring Catalina like that, even though it probably doesn't really need anything which isn't available on earlier versions of macOS. To the other question, it is only 4 pieces: name1.mts, name2.mts, name3.mts, name4. I dont see it jumping there while cutting, only after the copy process is completed. This page says 'OS X 10.10.0 or later', but when you go to their page the only 2.7.8 version of the app for macOS they have requires Catalina (and I did try to download it to see would it maybe run on earlier versions, but it just tells you that it requires Catalina or newer version of macOS). I now discovered that, if I choose a B-frame or p-frame for A or B that it will jump the markers to the next i-frame automatically in the resulting video.

Avidemux cutting video