Certainly don’t disagree. Loading times will be the biggest advantages of an SSD. With a SATA SSD, you’re looking about up to 5x faster than an HDD. With NVMe, you’re looking at 15X or more. In flight after all that loading is done, it should have zero impact.
EIther way, the cache location shouldn’t matter. The fastest source is always the most optimal, but it doesn’t mean that a slower HDD will harm cache performance. It’s likely as fast or faster than most users’ internet connection, and will have lower latency.
Personally, I don’t use the rolling cache at all. I manually cache areas I fly over regularly and disable the rolling cache altogether. I have gigabit internet. I don’t need it.