I have no idea what REQUEST does, but based on the documentation
I don't think sending the raw error template to the user was the
intended functionality -- but I couold be wrong.
It seems Coldfusion behaved as expected. The
livedocs
on cferror say two things. First, setting the type attribute to
REQUEST is a general way to get cferror to run when there is
"any encountered error". Secondly, if you set the type
attribute to REQUEST or to VALIDATION, Coldfusion will not be able
to process CFML tags. Makes sense, for the tags themselves could
generate further errors.