I don't think you misunderstood, I think they're talking out their arse. Modems don't run Linux, they run RTOS operating systems. ShannonOS in the case of the Pixel 6 with a exynos modem
https://www.telit.com/devices/fe990bxx/ - "High-performance quad-core CPU and Linux OpenWRT OS, ideal for router development without an external CPU"
Plenty of cellular modems run Linux.