No, the fix was to prevent dead ends to be longer than 6 rooms long. They even attempted to do that and almost succeeded.
To illustrate it be bit better for the map posted above, this is the main path, marked in green:
This is the same map, extended with dead ends marked in red:
The white numbers are the dead end length counters. If you mark several dozen maps the same way, NONE will have any of those counters go above 6. This isn’t just a coincidence, whoever designed Underspire intended this to be “fair”, there’s a fixed limit on how far you can wander off into the wrong direction. Allowing extra paths that can be arbitrarily longer breaks the whole design. You might as well drop the fixed limit entirely, because players can’t tell whether they are on a “normal” or “arbitrarily longer” path.
Which brings us to the bug. In some very rare cases the constraint check fails. It seems to be caused by the dead end branch being located on an outside border and entirely locked in by other rooms, except the very last one (with counter 6). The algorithm will then attach extra rooms to the very end, without first verifying that it doesn’t exceed the fixed limit.
This SHOULD be easy to fix, once you get “them” to admit that the initial fix may not have covered all the situations it was supposed to cover.