Yes, the lab cache will be added to the statistics (even if you found the most caches with lab cache in past). But the PGC premium status is checked on the day the profile stats are generated so even if you will see the lab cache there for the month of the trial, it will disappear after the premium will expire.
Again, you can check my stats and see that the lab cache is no longer there even though it was there when I was writing my previous answer last year.