Correct, the AsyncOS 6.5.0-45 is slated to be available for both the ESA and M-series(SMA, Security Management appliance):
AsyncOS 6.5.0-405 for Email and Management to all customers. This release applies to all our Email Security Appliances (C-Series and X-Series) and Security Management Appliances (M-Series).
It may be that you're on an older version of the M-series and you need to upgrade to a new version before you can see AsyncOS 6.5.0-045.
You should contact Customer Support and provide them the serial number of your M-series appliance and they cna verify the full upgrade path that your machine can get to.
the release notes state that its available for the M series, but when I try and upgrade its not listed.
