A lot of the people who didn't update their devices at all and jailbroke them didn't have battery issues like the people who had updates before the newer phones were announced.

Its suspected that Apple updated people's phones to start randomly shutting off after a certain date broke in one update, then made a second update after the new phones came out that slows the phones down to a crawl to incentives people to buy new phones and people who dodged the second update would have non-functioning phones. When they were caught throttling old phones with built in obsolescence, they said it was to keep a discrepancy in voltage of old batteries from making the phones shut off, but people with jail-broken phones that had no firmware updates from apple were saying none of their devices were experiencing that like the people who had updates before the new phone came out. Apple ended up being legally forced to replace batteries free of charge in some countries over a lawsuit from the whole ordeal, but people didn't have proof that it was tampering due to Apple's claims of the updates being functonality based.

Honestly, the fact that jailbroken phones didn't have the same battery issues is suspect to me. Even without the crazy conspiracy of questionably updating phones. It's pretty unethical having all options of functionality on a device lean toward upgrading due to malfunctions right as warrentees end so if they don't, they'll have to pay for proprietary replacements and repairs.