Isn't that a different tangent? Does it matter, when the SaaS codebase is same for all tenants? If you are dealing with different codebase for different clients, then that is a flawed approach in that it is error prone and not scalable as tenants increase in number.
Even big software vendors whose products auto-update, e.g. Chrome, have to support differing versions to some degree - even if it's just to achieve A/B testing, phased upgrade rollouts, etc.
Being forced to flip the switch for all of your users at the same time can make that an awfully big and scary switch you're about to touch.
trying running a single SaaS codebase for enterprise clients. Maybe you can upgrade everyone with CI on a single commit, but no line of business solution wants that. We have to run a very strict and explicit upgrade cycle for our apps that allows them to test extensively before committing to newer versions.
Just because you're SaaS doesn't mean your clients are...
It's not a 100% fail proof solution, but enforcing API versions in the the request helps. /latest/ is available in our preprod environment, but in production you can only call the API with an explicit version.
