It can have several benefits:
- More awareness of your baseline recovery, baseline fitness, and sleep patterns
- The ability to see subtle changes over time (HRV or RHR improvements)
- More accountability: Do you prioritize sleep enough, do you train enough?
- Being extra careful, when recovery is not up to par (data to show your coach, for example)
- Being able to make small experiments: Do I recover better when I eat vegan, or eat a late meal, use an Omega3 supplement, read in bed, etc.
The awareness and accountability part will not be that relevant to you. I know people who don't use the log feature, but the daily reminder of their fitness levels keeps them motivated. And seeing RHR decrease over time can help to make the habit of fitness stick. But after years of cycling you will probably not have much to improve here.
Point 5 would be the most useful feature for analytically minded people like you. I have run a couple of mini experiments over the course of 8 months and, after cancelling my subscription, sticked to my newfound habits and insights. Actually, I think whoop should focus more on this feature and improve it (the ability to run useful calculations is very limited).
For example, I sleep better when I eat dinner a little earlier, but then eat half a banana before going to bed. Reading in bed and using a sleep mask improve recovery noticeably. And drinking up to 2 glasses of alcohol actually increases my recovery (and goes south after 4 drinks).