"Usually PSA is much more strict on its grades than SGC especially with T206."
This is just completely wrong. I once attempted a 40 T206 PSA cross over of PSA 4, 5 and 6 graded T206 cards and only 30 came back graded by SGC.
(Of course, I put a minimum grade -- PSA is notorious for overgrading pre-war cards.) I could also give you countless examples/stories of PSA 5 graded T206 cards with wrinkles that SGC would never cross over. SGC is somewhat more lenient when it comes to moderate corner rounding and centering, but otherwise is the stricter company with respect to creasing, wrinkles, paper loss, glue residue, etc.
Your failure to put a minimum grade was a catastrophic mistake and the blame here should not be shifted to SGC. The fact that they have signaled a willingness to work with you on a group of them only confirms that their customer service is second to none.
Finally, the below T206 Cobb was submitted to SGC by me for a crossover. I submitted it in its PSA 4 case, with a "Min. 50" notation. SGC gave it a 60, which I always felt was the right grade. By doing so, they have affirmed for me that I need not crack my PSA cards out before submitted for crossovers.