I feel there's risk. When I was tempted to try, I thought back to the wave of Amex shutdowns in 2019. There were surveys and discussion on what caused it and if people did x, y, z. If there's another wave, for sure this would come up as a potential cause.
That wave turned out to be related to self referrals. Which worked at the time. You can also say that was their IT issue.
Amex apps have this in the terms:
"If we determine that you have engaged in abuse, misuse, or gaming in connection with this offer in any way or that you intend to do so, including if you return purchases you made to meet the Threshold Amount, we may not credit, we may freeze, or we may take away the Membership Rewards® points from your account. We may also cancel any accounts you have with us."
Once may be a glitch, multiple times they can certainly say gaming.
Something is fine with Amex until it's not. I ask myself if I'm willing to accept the worst case scenario. For now, I'm not. With Amex, the points will just be gone, if you're lucky maybe a tiny window to get them out. With Chase, at least historically they've allowed 30 days.