As a general rule it's a good idea to enable AAIP for all Windows VMs, not just ones running services where we have specific integrations (e.g. EX and SQL). However if this application isn't VSS aware, something you can confirm by looking at one VSS writers are installed, then you'll have to use your own scripts to handle getting the database into a consistent state using pre-freeze/post-thaw scripts. Also, rather than simply setting AAIP to ignore errors, I would look at what errors you received when it was set to required. By setting it to ignore errors your basically saying if you can't do AAIP, take a crash-consistent backup and proceed instead of skipping the VM. That could very well explain what you were told the database files aren't transactionally consistent.