ah, ok. lucky guess
my guess is starhub. Phone probably had some starhub customised firmware already loaded in, and then detected an update when connected to starhub via eight.
reminiscing on my old telco phones:
- my first android phone was an old motorola which had a starhub boot up splash page, and hardcoded starhub home page in provided browser.
- a few years ago, bought a 2nd hand phone with m1 and some sg govt apps in firmware. factory reset the phone, and it insisted on installing those apps. Cured it by flashing LineageOS