They probably don't have high concentrations absolutely (e.g. they're not going to be 90%+ PhDs) but it's probably still several orders of magnitude above your average industry role.
Even if you get a PhD your working career is going to be around 35 years. Add 5-10 if you're done after college, and even more if you're not doing college.
I think we need to stop pretending people are senior when they're 10-15% of the way through their career.
The r&d space is really interesting but very selective for obvious reasons. Just a PhD won’t get you in. You will need significant other contributions - eg the right publications in high impact journals, possibly internship with the companies themselves, the right advisor/PI that collaborates with the company, etc.
Whether it becomes a practical requirement, or formal requirement, would depend. If it's a high paid position, in a small research group, of an established field, then Ph.D.s are likely to be very important.
If its a position in a large research group in a new and fast changing field, then its likely to be more open to anyone with unusual or interesting promise, but still highly value Ph.D's.
As for fields: research in engineering, finance, economics, device physics, chemistry, biology, pharmaceuticals, etc. Anywhere the research involves highly technical knowledge, and a pre-existing track record of original thinking, personal initiative, that have produced objective results, are very important.
"Research" is a thought and project management meta/leadership skill, on top of being highly educated and talented in an area. Ph.D.'s provide the extra time and social context to fill out those skills and demonstrate a track record.
Deep research areas in computer science would be foundations of databases, cryptography, formal verification, statistical heuristics, core algorithms behind deep learning, ...
Since so many areas in computer science are relatively new, there is generally more flexibility in who might be considered great at research. The field includes many unusually creative individual practitioners who have produced great work without a Ph.D.
But Ph.D.s are still very much in demand and common for research positions in these highly technical, high value areas.