So TIBCO indicated that “Officially” No, it is not supported.
They did indicate that some other customers have installed it on 7.4 and did their own testing/certification in house.
They can certainly do that from a CA perspective but obviously CA Support reserves the right to indicate that as a potential cause if we cannot determine what is causing any particular issue.
Best way is to wait on how CA will handle it.
We very well could certify 7.4 with the next release of Jasper.