Yes, he is correct the trial is only for the 1st MAPD, if changed in AEP that right is given up. Wish I could find a link, but a couple of us ran into this last year. I don't think carrier's can change a CMS rule.
The CMS guidelines are the "minimum" rights a beneficiary has, the carrier can go above and allow a more liberal interpretation of the reg to suit them. Christian Fidelity, for example, used to take anyone, anytime, off of a MAPD if they have been on less than two years.
The Missouri GI law is another example. The law says same plan to same plan, F to F, for example. AARP allows a client to go from a G to F, C, N or any of their plans during their anniversary since they don't offer G. They are not required to at all.