According to MS Docs, implicit grant flow is not supported for mobile, so how is that the only thing this supports?

all the flows for msal are here
https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-authentication-flows

this is the one I am looking for and is recommended for mobile msal auth
https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-auth-code-flow