Update: I've confirmed this bug and it does seem to line up with the working theory of a server delay in response. Effectively flying in a direction will yield no yellow rocks, but if you turn around after a while you'll see many behind you are now yellow.
But if you sit in one place and spin for a while pulsing you'll see them start to pop in as well, because it's not about the direction, it's about how long you've been near the particular rocks waiting for them to turn yellow.
I recorded a video demonstrating the issue, and added to the issue tracker for this bug, and I'd invite you all to join in so we can get this sorted out.
Thanks!
Source: https://youtu.be/fqo_I4TYj1Q
And the issue tracker link
issues.frontierstore.net