Sorry for the delay, I have been trying to reproduce your issue here but unfortunately with no success. Are you using version 5.7 of the product?
Would you be able to run both the native and SVR restores again with some extra SQL Server logging turned on for comparison?
Execute the following against the master db:
DBCC TRACEON (3004, 3605, -1)
Run a native restore followed by an SVR restore.
Turn off the extra logging:
DBCC TRACEOFF (3004, 3605, -1)
I would like to know if there is a specific part of the restore process which is taking the extra time, such as the recovery phase.
Test Engineer, HyperBac