So for jobs, ML/AI is pretty much an even field unless there are niche research jobs which only requires Phd gradudates
Physics/Math is useful but your particular field/speciality in CS is relevant as well. I would bet a bit more money on a CS grad to understand convexity, comp geometry and optimization than a physics grad, and math majors don't always have the code skills to develop things for production.
Point of argument here being frequently neither do CS Phds and at tech companies you pair Math/CS Phds with 'production' engineers.
Also certificates aren't really rigorous necessarily and also are quite easy to one-off versus relevant programs/theses/research experience.
production is an overloaded term depending where you go
[1]https://github.com/antirez/neural-redis
[2]https://twitter.com/Mikettownsend/status/780453119238955008
http://techcitynews.com/2014/08/07/big-data-is-a-lot-like-te...
And I think what I perceive as your doubts as to landing a job with one of these are probably founded. This is a way for the university to make a bunch of cash. As long as that happens, whether students get a related job or not is not important to the university except to help with marketing to prospects.