That's placing an awful lot of faith in this third-party website doing what it is intended to do, as opposed to other possibilities such as it not doing much of anything at all, or worse yet, exposing your data at some point.

Instead, my approach whenever I receive junkmail is:

1) I write to the sender to request that all of my information be removed from their databases and that I did not consent to receiving any information from them.

2) I file a report with the Better Business Bureau: https://www.bbb.org/file-a-complaint

3) If they have a public-facing presence on a site like Google Reviews, Yelp, and so on, I leave a review detailing that this company sends out spam.

4) And most importantly, I keep a spreadsheet of companies that have sent me spam, and try to avoid ever giving them any of my money or labor.