I don't believe that anybody is advocating running a fire system test in the middle of the memory items, or interrupting a checklist to do so. The suggestion was to do the fire test at some stage after the fire warning has ceased, in order to ascertain whether the fire has indeed been extinguished or perhaps the warning has stopped for other reasons. This is something I have never heard of before & never considered, but it does make a lot of sense to me after thinking about it for a while.
Perhaps some should endeavour to step away from the trees & take a look at the forest. And don't always hang your hat on the training you have received. Sometimes it is a case of the blind leading the blind. The status quo is not always correct & it is often wise to consider new things objectively, rather than just repeating the mantra - "we have always done it that way"