Identical hardware. Virtual machines, and same SSD / Raid type on the SAN.
Looks to me like this is actually by design.
The Log is always being restored to the Mirror database in recovery. If it didn't do this failover would have to complete a Log restore. (This still happens, but it's only from the unrestored LSN, not the full log)
A full Log restore would make failover take minutes, not seconds.