According to
THIS it's about 90% of Blinn Team students convert to being A&M students. I can't find anything for Gateway that is reliable but it is likely similar or higher.
Those programs target kids from excellent HS's that get screwed by the Top 10% rule but typically have lots of APs, Dual Credit, and good SAT scores that typically are well prepared for college. I know many kids that have done both and I don't know of anyone who didn't get in, though I'm sure it happens.
They almost certainly are more successful than regular admits percentage wise because those include a lot of Top 10% kids from underperforming HS's that otherwise aren't well prepared for college and are often not used to being away from home or the academic rigor of being in a Chemistry class with 400 people and a prof that barely speaks English.
It's basically a backdoor way that A&M can try to boost 1st Gen and Diversity stats while placating kids from strong HS's that can't get direct admission to A&M (many related to alumni). It's all a shell game.
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Ronald Reagan