Tag quality timestamp

We have a Tank overview screen that’s listing several tank properties in a table.
There is a refresh date/time column that’s showing the value timestamp on one of the tags to display when the readings happened.
When the tag is disabled, the timestamp is continuing to be updated when the screen refreshes. I didn’t expect that timestamp to be updated when the tag is disabled.

I tried to read the .LastChange attribute of the tag, but that is None when the tag is disabled.

Is there a way to know when a tag quality goes bad or disabled? What does the timestamp on the QualifiedValue actually represent?

I found a useful discussion here: tag.readAll returns different quality (vs tag.read) which is many years old and says issue was fixed in 7.6 (currently running 7.9.8)

I did a comparison with readAll and read and found the timestamps are different. read gives the correct value, readAll is showing “current”

qv =system.tag.read('[default]tank/tank_018/TkTemp/value')
aqv = system.tag.readAll(['[default]tank/tank_018/TkTemp/value'])
for x in aqv:
	print x.quality, x.timestamp 
print qv.quality, qv.timestamp

Output is:
Disabled Fri May 31 18:15:12 EDT 2019
Disabled Thu Jan 10 00:53:30 EST 2019

So issue quality attribute was fixed and timestamp is still different?