Usually its suggested that
Using multiple backup devices for backup and restore operations enables SQL Server to use parallel I/O to increase the speed of backup and restore operations because each backup device can be written to or read from at the same time as other backup devices. For enterprises with large databases, using many backup devices can greatly reduce the time taken for backup and restore operations. SQL Server supports a maximum of 64 backup devices for a single backup operation.
this is the opposite of the way you are doing it, so yeah restoring 2 database from the same media device will effect performance because IO operations are happening on the same disk at the same time.
Copying the data and transaction log from the backup devices to the database and transaction log files is performed by reader/writer threads; one thread is assigned to each backup device.
performance increases with the number of backup devices
and in your case its the opposite, so Performance decreases if you are using 1 backup device to restore 2 different databases
for more on Backup and Restore Performance in SQL Server check section Using Multiple Media or Devices
So i guess the answer to your question, is
Its possible to restore 2 databases from same file but not Wise