Looks like the transition is possibly not in the correct place between the two routes. Here's what GSV shows @ that intersection:
SB ON-12 &
NB ON-12And here's @ the 'southern' JCT of ON-11/12:
https://maps.app.goo.gl/4eGTc6icVQDXPpUz7So, some more research needs to be done here.
Thanks to yakra for bringing this to my attention via PM.