I agree that RH 7 behaves as you say.
[ I thought I could demonstrate that tags get lost on first
conversion to RH 7. It turns out that in a particular project, the
tags were no longer in the RH 6 project manager before the
conversion. But for some reason they were in topic code as META for
a topic, and as conditional text tags. ]
In RH 7, at least, if you delete a build tag, it is deleted
everywhere it had been applied.
I do have one anomaly to report.
If you start a project in RH 7, and you import source topics
from a RH 6 project with build tags, they do survive in the code.
That is, they are not stripped out.
RH records the incoming tags in the cpd database, in a table
that lists build tags, and in another that lists topics and their
properties.
However, the project manager doesn't show them until you
re-create the incoming tags.
Oddly, incoming text-level conditional areas are shaded in
the RH 7 topics, if you have that option selected. If you have that
column showing in the topics pod, they are listed even when the
build tags pod doesn't show them.
Harvey