Going to chime in on this one:
Background...long time DIS person (esp on Transportation), over 30 trips to WDW, and the majority of those using DME--with the yellow tags with not one problem.
Went for a short Food and Wine trip 2 weeks ago, and since I added my sister to the reservation only a few weeks prior, the DME info we received only covered me, as far as luggage tags. Which...since we got 2 Magic Bands, and I knew she was on the reservation, I hadn't looked at when that envelope arrived in the mail, assuming both tags were in there.
Morning of flight, discovering one tag, we had the choice of...do I just carry on my bag (it's a legal carryon), or... do what I see is possible on the DIS and just give them my tag number (I let my sis use the yellow tag) when we check in for the bus.
So...hey, let's test the DIS info... I'll check the bag and see how well the process works.
The reality--yes the bag gets there, but also, that bag does get delayed. And they will tell you that it will take longer than the tagged bags. They get the luggage info (not by size/color, but off of your baggage claim check) and eventually get your bag. Sister's bag showed up on time, but mine was delivered at least 2 hours after hers--at nearly midnight after a 5:30 pm-ish plane landing/resort check in about 6:55 pm.
So....it works without the yellow tag, but it doesn't work as well as WITH the yellow tag. If this happened in the future, I would either carry on, or go get my bag. (or check the envelope ahead of time and make sure I had both tags).