Never used withPOSTData, I’ll have a look, but as I wrote, we have always just used withParameter and never had issues until the latest commits.
The description of withParameter is
Returns a copy of this URL, with a GET or POST parameter added to the end.
Passing true to createInputStream should be more than enough.
doPostLikeRequest if true, the parameters added to this class will be transferred via the HTTP headers which is typical for POST requests. Otherwise the parameters will be added to the URL address. Additionally, if the parameter httpRequestCmd is not specified (or empty) then this parameter will determine which HTTP request command will be used (POST or GET).