The in-house cellular modem part was pretty well known years back. In fact Apple had started poaching heavily from Qualcomm back in 2017 IIRC.

In 2016, many Qualcomm Modem folks moved over to Intel Modem Division in San Diego with higher pay packages and then became Apple employees once it got acquired.

The poaching continues to this day because, as you know it, Apple has very very deep pockets . Apple also recently established thier offices in SD, including a big campus in Rancho Bernardo area - thereby signifying that they are investing heavily in talent in the San Diego region - which has traditionally been seen as Qualcomm’s backyard.