If you have reason to suspect that the job market will be somewhat recessed in the coming time then getting a PhD might be a reasonable strategy to ride that time out.
It's the opposite. R&D is a long term investment. When a company starts a new project in a recession then the recession will be over by the time the project has been completed. When a recession coincides with the completion of a project then you can't travel back in time to undo the decision.
Recessions generally hurt companies that sell directly to consumers the most. Business to business companies are usually affected the least.
I think the idea is that you spend the recession years in a relatively safe albeit badly paid position which can potentially lead to more lucrative opportunities in the post-recession years. This makes some sense except that your skill in predicting recessions is likely horrible and you probably shouldn't be planning your career based on it.
Some years ago I remember somebody (maybe Tim Bray) had a post that the people who had the best careers in Tech would go to secure government positions during recessions, where they would generally work on crafting the standards other people would have to follow, after the recession they would move into a period of private consulting on the standards they had just designed. I think the PhD argument is a variant of that.
It is of course correct that if you are so good at predicting recessions that you could use this strategy effectively then probably your best monetizing possibility would be just predicting recessions and investing based on that. But then it is not sure that people will do the most effective thing either.
PhD's tend to work in advanced areas of companies. When recessions hit, R&D is one of the first places to take a hit.