In fairness to CGC, they're very busy right now with demand for their services.
I submitted in person at WonderCon at the end of March for an 8 book Economy submission.
It went to SFG in the system on 4/11 and has been there ever since. When it hit the system that day, the TAT was 32 days and had dipped to 28 days about a week later. Now it's up to 54 days estimated TAT for that tier submission.
The books are on their 38th business day in CGC's system tracked possession, beyond what the original estimated TAT was when they were entered in the system.
Reasonably, the estimate is just the estimate. Based on my current experience, I would estimate TAT based on what the current, estimated TAT time is not what it was when entered in the system as it will always be fluid on the lower priced tiers based on demand/staffing.
These are books for my personal collection that I wanted slabbed and I can be patient getting them.