Content type level workflows are a thing which has been very common in SharePoint world for many years. However with introduction of new workflow platform in SharePoint 2013, significant changes were made which resulted in few limitation been introduced for content type level workflows.
Please note that as far as AgilePoint NX is concerned this article applies to Office 365 workflows only and content type level workflow association works for SharePoint OnPremises even in SharePoint 2016.
One thing is pretty clear that Microsoft did not intend to add support for addition workflow association anymore at global content type level which they have already documented but I know that Microsoft is under pressure to bring this feature back.
Please look for following line in the article
“Unlike previous versions, SharePoint 2013 does not support workflows that are scoped to a content type (SPContentType). “
Now regarding content type added at list level and associating workflow with content type within scope of the list and not at global level, last we checked it had plenty of bugs and even though it is visible on UI it was not accepting 2013 style workflows and were failing. If you look closely even Microsoft’s own workflows on list level content type are still 2010 style. Not a single one is 2013 style and that is why I am sure situation is still the same. As you know only Microsoft can push 2010 style workflows in O365. Vendors have to do 2013 style workflows
I know Microsoft is trying to work on it still and might change soon but capability is not available from Microsoft itself as of now.
Also even other workflow vendors in Office 365 cannot support content type based workflows due to same reason. This might change as Microsoft might be close to reintroducing this feature in near future but as of today it does not work.