I can't think of anyway on the spot of how this could be abused. They still don't know who you voted for, just that you voted. Are there any common abuses of this data?
We use envelopes here to hide the ballot from the people in charge of the voting slot. We can put an empty envelope, or with ballots of two different parties that make it void, or with a nasty letter about the policianos, or like in Brazil where they "elected" a rhino for major https://en.wikipedia.org/wiki/Cacareco
Just don’t enroll in a political party. Political people want to turn out votes for them.
In states with a closed primary that has some blowback. Where I grew up, the Republican primary was the election. Where I live now, the Democratic primary is the election - the only GOP candidates are clowns with no organization.
Sold to ad tech agencies who can match it with whatever other information about you they already have. It's a binary yes, no, so maybe abuse is too strong a word. There's limited use.
Being forced to write down support for an entity that you don’t want is a psychological hack.
Now you can’t just tell the “vote or die people” that you already voted to get them off your back.