Ng-disable doesn't work on ion-checkbox when based on the model of a ion-toggle when in a tabbed app?

ionic-v1
1

I made a small example at

to demonstrate my issue. In codepen, I’m able to enable/disable an ion-checkbox by setting the ng-disable=“modelSetByIonToggle”. However, in my tabbed application, it won’t work. The ng-disable seems to be ignoring the model.

Can anyone figure out what I’m doing wrong?