I'm ready to grant that you found an occurrence in the wild but it takes more than that to demonstrate prevalence, conventional usage, or semantic fidelity to originally intended meanings. Also they are appealing to a usage that's practically as old as the paradigm of personal computing itself, so I don't think they're the one that's out of date.

I happen to remember "sideload" as a term of art for some online file locker sites to mean saving it to your cloud drive instead of downloading it to your computer. A cool usage, but it never caught on.

I think nomenclature as it exists in the PC software universe is closest in spirit on all fronts, in describing running software as, well, running software, and describing installing as installing. While a little conspiratorial in tone they're not wrong that "sideload" pushes the impression that controlling what software you run on your phone should be understood as non-default.