The blog article doesn't actually say the IAKERB impl will proxy to KDCs. Strangely it is entirely specific to Windows 11 and by extension Windows clients. There is no mention of Windows Server. So it's not crystal clear to me that the implementation will be able to authenticate domain accounts. Maybe it will only authenticate against the "LocalKDC" on top of the local SAM just to work around the issue of being able to log into a machine without line-of-site to a KDC (or NTLM or VM console) and nothing more.