flanged plungers typically dont fit sink drains and will deform upon compression, and sink plungers dont create enough of a vacuum seal in the toilet outtake to be of much use without a lot of unnecessary effort and mess.
If the clog is severe, then you'll make little and often no headway using a flanged plunger on a sink drain or a sink plunger on a toilet, no matter how long and frantically you thrust away and splash about.
the flanged plunger isn't rigid enough to create the necessary vacuum or pressure in a sink and the sink plunger doesn't create a tight enough seal to create the necessary pressure in a toilet unless the clog is mild in the first place.