

It could also be something less alarming, like cellular repeaters inside the building. Many buildings use these to boost indoor coverage when concrete and steel block signals from outside towers, and that might explain why your phone flagged multiple connections so quickly. I’m not ruling out the possibility of a rogue tower or IMSI catcher, but it’s worth considering that the alerts could simply be repeaters being picked up by this new warning feature. Either way, it’s good that your phone is making you aware — at least now you know when unusual connections happen.
That’s true for some types of signal boosters, especially the simple passive ones. But many building systems aren’t just passive repeaters — they use distributed antenna systems (DAS) or active repeaters that re-broadcast the signal from outside towers. From the phone’s perspective, those can sometimes look like a new connection point, even though they’re not rogue towers reading data.
So while your point is absolutely right that a normal repeater doesn’t act as a tower or capture phone info, the way modern indoor coverage solutions are implemented can still trigger the same kinds of warnings. That’s why it can be hard to tell apart a harmless booster from something more suspicious.
More information about DAS systems and cellular repeaters, and how they differ, if you’re interested:
🔗 https://en.m.wikipedia.org/wiki/Distributed_antenna_system
🔗 https://en.m.wikipedia.org/wiki/Cellular_repeater
(edit, added Wikipedia links)