I don't think Google is in the wrong here:

If you have a route between two points 'white dots' appear in the route, then you can drag and drop those around to manually change the route, to share the URL you can either copy the url at the top bar or just click the 'share' option inside the hamburger menu, which gives you a minified link.

In the end, although it's an inferior(?) implementation, Google allows you to do the exact same thing. I think the ToS call mentioned is essentially appropriate.

Although it is a bit of a dick move, but in the end it is their api.