Honestly, it might be worth upgrading to V5 if you’re having issues with V3… V3 only has a little over 6 months left in it’s life cycle anyways…
Off the top of my head, I believe with V5 (and maybe V3, been a long while since I’ve looked at those docs), each endpoint in REST only has one eligible method (GET, POST, PATCH, etc…), so explicitly sending it in the URL is rather moot