While chlorine bleach may damage polyester to the point of failure, it won't remove the dyes.

The bleach/sublimation shirts you see are cotton/ployester blends. Specifically, they are heather colors. In such shirts the cotton fibers contain dye, but the polyester is clear (looks white) and is what gives the garment the "heathered" look. The bleach removes the dye from the cotton fibers, and then one sublimates the polyester fibers. Once washed, any sublimation ink on the cotton fibers will come off, so don't judge your results until after washing.

Note, not all cotton dyes can be removed with bleach either, depends upon what dyes were used.

People often use the HEATHER colors of Gildan 64000 (sometimes called G6400) Softstyle shirts. These are 65% polyester, 35% cotton. Don't use the sport gray, as it is only 10% poly. Don't use any of the solid colors, as they are 100% cotton. Don't use any of the antique colors, as they are only 10% poly.

 

I tried to bleach a 80% polyester and 20% spandex for sublimation but would not bleach.

In short... bleach will not work on dyed polyester.
Bleach will only work on most cotton dyes.