SSD isn’t necessarily less energy hungry than spinning platter.
It really depends on the specific units and use patterns.
Generally SSD has better idle power, and HD has better read and write power, but that doesn’t even always hold true.
If your device sits idle long enough, SSD is better for power, but the write time to get to idle could easily consume the power differential.
https://www.edn.com/power-vs-energy-ssd-and-hdd-case-studies/
At idle, SSD is usually better (like you said if the SSD has proper power management, and that takes research to know).
Spinning platters are generally still better for power per gig/terabyte, because write time they consume less power than SSD.
I dont really look at drive power consumption, because even with ~10 drives running in my environment, a single cpu doing anything moderate blows away their power consumption numbers (I’ve tested, not that it was needed, heat dissipation alone makes it clear).
I have a ten-year old 5 drive NAS that runs 24/7, and it’s barely above room temp. Average draw is a few watts (the number was so low I put it out of my mind, maybe 5 watts - Raspberry Pi territory).
My SFF desktop is 12w at idle, with either 2 small SSDs (500GB each) or a single large drive (12TB). So much for SSD having better idle power.