Why would a veterinarian advise me to run a FELV test, knowing that the cat was exposed to a, possibly infected kitten?

I found 2 kittens of diffrenr ages. I had them in the same room for a couple of days. I'm aware that if one had FELV that the other could've been infected. I had taken the younger kitten to urgent care.It was not old enough for the test.

A couple of days later, I brought the older kitten and I was told that he was old enough to get a reliable result, although I don't think he was. The only reason I was concerned is that I havr other cats, and, if the kitten was negative, I could have started introductions.

However, seconds after the test was run, I was told that l, if the cat had been exposed to any infected cats within the past 2 weeks, the test would have to be repeated in a month.

Knowing that I'd only found the cat a few days ago, and, that it was exposed to an untested kitten that I'd found at the same time, why did the vet advise me to run the test?

Had this information been disclosed before I agreed to it, I never would have spent the money on an inconclusive test.

To me, this was either a deliberate omission, or a serious lapse on the part of the vet. The vet had all the facts necessary to tell me that the results wouldn't be completely accurate, so why would she tell me to run the test? It served no purpose.