This can be as “simple” as your phones being in close proximity to each other for an extended period, and sharing device advertising IDs/other device data via WiFi, Bluetooth. Might be more to it, but it’s a likely factor.

Devices do this regularly btw, smartphones also scrape for WiFi networks to better geolocate etc.

In this case, I think the creator just avoids Telegram, for good reason:

It’s not E2EE encrypted by default.

The list is not named appropriately “US etc” but it’s not a bad list either