Safely sub allocating dynamic IPv6/64 network to multiple VLANs
This post is deleted!
I determined that sometime in the last year my ISP (Cox) made it so I can send a hint for a 56-bit prefix and use track interface to obtain a separate /64 for each of my VLANs. This didn't work a year ago but it does now.
Oddly enough Cox tech support still says they only issue 64-bit prefixes. However that's not what I am seeing now.