I should've clarified:I am surprised that you think the IRST21 is some kind of marketing pitch.
The claim that the IRST21 was developed to deal with J-20s is what seems like a marketing pitch. I'm sure its a top tier IR imaging solution, and mounting it on a drop tank is genius. But IRSTs can't make Gen 4 competitive against Gen 5 by themselves, as I'm sure you already know. This myth was recently fueled by Russian and Indian sources. Russians claimed their Su-35s could target Raptors in Syria, while Indians claimed their MKIs can target J-20s over Tibet, using IRSTs... it's just propaganda.The IRST21 development was to target the J-20.
Getting back to the topic, I still hope the Block III gets a podded IRST, as it does increase the tactical options and also speeds things up with IFF ROEs. Having 1 Thunder equipped with IRST in a group of 4 should be good enough for our use case, I would think. Integrating it on the airframe would actually be counter productive