VST3 resizable plugin always scales to window size in some hosts

I noticed that our resizable VST3 plug-in changes it size to fit the hosts plugin windows when opening the UI. I was able to reproduce this in reaper and a user reported something similar in cubase.
VST2 does not have this behaviour and takes the size we set in the constructor of the main component. Is this expected for VST3 or do i miss something?

I have found this thread about something similar. I will try this.