Medicare rules keep changing as GOP keeps attacking USians who aren't rich.
So don't just memorize what someone toots - as you get closer to retirement age (or if you're disabled and qualify for SSDI or SSI), check Medicare's own site (check the URL carefully...don't just trust top hit in crappy search engine) for what the current rules are.
But they definitely do harsh deadline punishments. https://mastodon.social/@limebar/112898317468767925