Hmmm, this is interesting!
The link you posted is for WebLogic Server, so I suppose that this requirement is specific for this implementation of the container, because I made a quick check in the
Servlet specification 2.4. and there it is stated that sub elements in <web-app> tag can be in any order:
SRV.13.2 Rules for Processing the Deployment Descriptor
"The sub elements under web-app can be in an arbitrary order in this version of
the specification."
Maybe someone else with more experience can confirm that.
Regards