trouble getting wx.TextCtrl contents to re-center on resize

I have a TextCtrl with style=wx.TE_CENTRE, and I want/expect its contents to remain centered when I resize the TextCtrl. However, the text stays on the left side of the TextCtrl.

import wx

class MyApp(wx.App):
    def OnInit(self):
        frame = wx.Frame(None)
        frame.Show(True)
        self.SetTopWindow(frame)
        self.myText = wx.TextCtrl(frame, value="A", style=wx.TE_CENTRE)

        sizer = wx.BoxSizer(wx.HORIZONTAL)
        sizer.Add(self.myText, wx.EXPAND)

        frame.SetSizer(sizer)
        sizer.Fit(frame)

        self.Bind(wx.EVT_SIZE, self.OnSize)
        return True

    def OnSize(self, evt):
        self.myText.SetValue("after resize")

myApp = MyApp(0)
myApp.MainLoop()

After a lot of trial and error, I got it to work by doing both of the following:

• Refresh the TextCtrl in my wx.EVT_SIZE handler
• Add the style wx.TE_RICH to the TextCtrl

Why are both of these necessary? I'd like to understand what I'm doing wrong here. (I'm using wxPython 4.0.4 on Win7.)

It may be your environment, it certainly works normally on Linux using wx 4.0.4
It could be down to the fact that you are doing it all within a wx.App class.
Conventionally this code would be written something like this:

import wx

class MyFrame(wx.Frame):
    def __init__(self,parent):
        wx.Frame.__init__(self,parent,-1,("My Frame"), size=(200,100))
        self.myText = wx.TextCtrl(self, value="A", style=wx.TE_CENTRE)
        sizer = wx.BoxSizer(wx.HORIZONTAL)
        sizer.Add(self.myText, wx.EXPAND)
        self.SetSizer(sizer)
        self.Show()

myApp = wx.App()
frame = MyFrame(None)
myApp.MainLoop()

Does this code misbehave in the same way?