In fact, short of a rec pilot taking the initial remote pilot exam, I believe there’s no restriction on their taking the recurrent exam. (I think) Anyone can do it, its free, the subject areas are weighted a little differently than the initial exam, but one could learn a lot going through it, including the latest regs on night flying and Operations Over People & vehicles. It’s a lecture, study guide, and quiz/test all-in-one.
You make a very good point and in fact it's worded that way on the page description for the Recurrency Course:
ALC-677: Part 107 Small UAS Recurrent
Part 107 sUAS Recurrent – Non-Part 61 Pilots Introduction
The FAA has developed regulations to allow the operation of small unmanned aircraft systems (sUAS) in the National Airspace System (NAS) for purposes other than limited recreational use. The rules are specified in 14 CFR part 107 and address UAS classification, certification, and operating rules.
This training is designed for non-part 61 pilot certificate holders (or those without a current flight review in accordance with 14 CFR § 61.56) who wish to remain current as a part 107 remote pilot with an sUAS rating.
Others may take this training as a self-study resource, including:
- Aviation Safety Inspectors (ASIs)
- Anyone interested in learning more about 14 CFR part 107