It doesn't say a person has to be "indefinitely confined" to receive and cast an absentee ballot. It says they have to be "indefinitely confined" to have "an absentee ballot be sent to the elector automatically for every election" and this particular category of absentee ballots "shall be clearly marked as not forwardable" (not the case with absentee ballots requested for a specific election date, as those are intended for people who will be out of town, e.g. for work, and may need to have the ballot forwarded in order to receive it).
The linked tweet is implying that this is the only category of WI absentee ballot that doesn't require ID. I still haven't seen any proof of that. It also doesn't explain exactly someone does with an ID when voting absentee (I think in many states, it just means putting your driver's license or other state ID number on the ballot envelope, which only means the person completing the ballot envelope needs to know the ID number for that voter, not be that voter -- theoretically, the workers processing the ballots could check these against the voter registration info to make sure they match, but I expect that happens even less often than meaningful signature-match checks).
Words matter. u/airgag helpfully posted the actual language in the statute you are referring to: https://thedonald.win/p/11QRyJY7Zx/x/c/4DpKSoLI2FE
It doesn't say a person has to be "indefinitely confined" to receive and cast an absentee ballot. It says they have to be "indefinitely confined" to have "an absentee ballot be sent to the elector automatically for every election" and this particular category of absentee ballots "shall be clearly marked as not forwardable" (not the case with absentee ballots requested for a specific election date, as those are intended for people who will be out of town, e.g. for work, and may need to have the ballot forwarded in order to receive it).
The linked tweet is implying that this is the only category of WI absentee ballot that doesn't require ID. I still haven't seen any proof of that. It also doesn't explain exactly someone does with an ID when voting absentee (I think in many states, it just means putting your driver's license or other state ID number on the ballot envelope, which only means the person completing the ballot envelope needs to know the ID number for that voter, not be that voter -- theoretically, the workers processing the ballots could check these against the voter registration info to make sure they match, but I expect that happens even less often than meaningful signature-match checks).
In WI, to obtain an absentee ballot, you are required to provide a scan of your driver's license with the application.
Indefinitely confined voters are exempt from that.