Incompatibility of TCustomForm.DoShow in Lazarus 2.2

[tetrastes]

I have a working program, which was compiled with Lazarus 2.0.8. After compiling with Lazarus 2.2.2 it didn't work as expected. 
I found that this is due to incompatibility of TCustomForm.DoShow. In Lazarus 2.0.8 (and in whole 2.0 branch?) the definition is

Code: Pascal  [Select][+][-]

1. procedure TCustomForm.DoShow;
2. begin
3.   if Assigned(FOnShow) then FOnShow(Self);
4. end;

while in Lazarus 2.2.2 (and I suppose in 2.2.0)

Code: Pascal  [Select][+][-]

1. procedure TCustomForm.DoShow;
2. begin
3.   if FIsFirstOnShow and (WindowState in [wsMaximized, wsFullScreen]) then
4.     Exit;
5.   FIsFirstOnShow := False;
6.   if Assigned(FOnShow) then FOnShow(Self);
7. end;
8.  

This is reflected in CHM help, but not in online help, and not at https://wiki.lazarus.freepascal.org/Lazarus_2.2.0_release_notes#LCL_incompatibilities, though this obviously can break existing code (as it happened to me ).

So I wonder, what are the sense and purpose of this change, and what is the difference between normal and maximized window, except size?