I can not confirm that bevaior. If I add a line in that memo, it scrolls automatic to the last entry.
For example, use a empty form, with a memo (Scrollbars=ssAutoVertical) and a timer:procedure TForm1.Timer1Timer(Sender: TObject);
begin
Memo1.Lines.Add('Test '+IntToStr(Random(1000)));
end;
I use Win7 64bit, tested Lazarus 1.0.14 and 1.3Trunc - same behavior.