Wow, so this is weird. Thanks for your answers, but I think my AP might be acting a bit strange. Unless any of you want to do this test that I did to see if it's supposed to act this way-
Opened up a CR2 raw file. Pulled up my 16:9 crop preset, and it stayed constrained to 16:9 if I pulled one of the borders or corners. I tried it in both the Develop and Photo personas. Cool, that's what I wanted.
Then I did a test with a jpg, in Photo persona, I pulled up the 16:9 crop preset which made the little rectangle, and that 16:9 custom preset remains constrained when I adjust the size. But when I apply any of the built-in presets, all those are unconstrained. Very odd.
I'd make a screenshot video of what I'm seeing, but I forgot to bring my mouse to work with me tonight. Much easier to do with mouse. Maybe I'll make one tomorrow.