Stop requiring AssertionConsumerServiceURL parameter inside SAML requests

As explained in OASD-27648, the OpenAthens IdP requires SAML requests to identify the SP’s “AssertionConsumerServiceURL=” or else OpenAthens will throw the following Bad Request error: “Could not establish assertion consumer service url for…“

OASD-27648 suggested that the SPs make adjustments on their side to start including AssertionConsumerServiceURL inside their SAML requests. However, that would put extra responsibility on SPs, and it might require development work on their end which could take months/years, or they might not be able to accommodate it at all. In either situation, our customers are unable to use OpenAthens with those resources.

With this being the case, I notice in OASD-27648 that “the SAML spec we use mentions ACS in the AuthN request is optional”. Since the inclusion of AssertionConsumerServiceURL is optional and not required, would it be possible for OpenAthens to stop requiring it in SAML requests?