I just poked around on the web. I find the rule on the Marriott site saying only 100,000 points can be moved out of an account in a year:
Share your points
Now you can share your points with any other member.
Transfer 1,000 points or more—up to a maximum of 100,000 points per year.
https://www.marriott.com/loyalty/redeem.mi
Best of luck to you on finding a workaround. At first glance, it seems pretty rigid.