I don't think that this thread was ever in danger of being shut down if it remained on (the OP's) topic.
But as Ian pointed out above, any time that issues of scanning are tangential to a thread, they can and sometimes do become the primary focus of the thread, in which case the thread is vulnerable to being shut down.
As an example, if the thread became about which lab does the best scans, it would probably be shut down.
APUG's exclusionary rules do serve a purpose, but they also have an attendant cost. The balancing act continues.