I agree 100% with popa.
Most shadchanim make shidduchim to help people out and it is only menchlichkeit for someone to follow up and let the shadchan know what is going on.
It is very questionable if they are doing just to help people out, and letting know what is going on means just how it’s concluding, not what motivated the decision how to conclude. And saying that they have a right to demand to know because “they deserve know”, it’s called blackmail.