yes. "Most of their competitors... prefer security through obscurity"

Count Texas Instruments ("TI") in this camp.

For example, Josh Wyatt of TI is proud of TI's "black box" approach to security, and even became a bit defensive about TI's closed source / "you don't need to know" aspects of its security for its CC3220 chips:

https://e2e.ti.com/support/wireless-connectivity/wifi/f/968/...

Why the F would anyone use these chips, when you can use a garden variety MCU, use a good TLS stack like WolfSSL or BearSSL, and fully control / own what goes into your product?