Only one person reported the spam call in that thread, the Marcus-II commenter. Their comment shows up twice in the first page and once on the second page. No one else mentions the spam call.

The baseband processor is entirely separate, with some basic commands and responses communicated from the phone's CPU to the baseband, so even this explanation is suspect.

No one is burning a baseband 0day to write "we are in control" on a screen.