Model changes which are ultimately JSON changes will cause errors far downstream in an Angular app.

There is no real type safety in JavaScript in spite of how much TypeScript will have you believing that there is. If a type hydrated from an API call is supposed to be a number and you get an object instead the code won't blow up until you do something later on like try to run the number with the CurrencyPipe. It is a little tricky to put your finger on exactly what went South quickly.