The issue is actually described here:
Fuse is not deploying latest snapshot version of bundles - Red Hat Customer Portal
https://access.redhat.com/solutions/2097131

The problem is that the proposed solution works only once after etc/org.ops4j.pax.url.mvn.cfg is
updated with the new property. Then it stops working, i.e it works for the first update but not
after that.

It uses the local m2 repo for the user running Fuse (e.g fuse_user) located in
/home/fuse_user/.m2/repository)!
In 6.1.0, it did not and always fetched from Nexus when we ran an bundle update for a snapshot version.
And here is why this is a problem:
The first time one installs a bundle (say 302), if it is not in the fuse_user user local m2 repo (in
/home/fuse_user/.m2/repository), it will fetch it from Nexus, put it in the local user repo and
install it in
Fuse.
But if a little later you update your bundle and deploy it to Nexus, go to your karaf console
and run "update 302", it will find it in the local repo and not download it again from Nexus even
though a newer snapshot version exists there.