This is very strange. I have just done exactly that in our store and, like @mr-papa, I definitely get version 5.7.5.2 downloaded. As it should be.
However, as @mr-papa said above – WordPress is having some problems with updates and it is possible that the updated data file that informs what SP update is to be downloaded has not been refreshed on your install (using the WP update problem) because of the WP problem. So try this…
Go to the forum admin > toolbox > housekeeping and click on the task to flush the XML cache. See if that corrects the standard update from the wp dashboard.