You’re probably right about the absentee ruse. I moved from North Carolina and received a notice cleansing me from the voter roles after they discovered my address change at the Post Office. This was surprising as NC has about the most lax voting standards anywhere, no ID needed. My daughter has lived in FLA for about 10 years and was only cleansed from the roles when they did my address check this year. (She didn’t vote in NC during that time anyway, but there are probably many who do.)
And I was talking about snowbirds, defined as people who maintain a residence up north as well as in Florida, rather than people who moved and gave up their old residence. Also, people who have vacation homes, students who still maintain their parents address as their permanent residence while living on campus, etc. No "change of address" notification to the Post Office would have been issued in the above cases.