Sometimes things are used because they are the best available at that time. This whole switch to Daddario strings smells of that to me. IF Daddario COATED strings had been equal to or better than the Elixirs (chosen because of the large volume and the fact that Taylor wanted their guitars in the showroom to look and play better for longer) then they would have been chosen then. Now that they've released their XS line it's clear that Taylor feels they're superior to their old supplier and made the switch. Nothing nefarious or misleading about that at all. Just don't stand in the rain and tell me I'm peeing on your leg (and don't complain you're getting wet because you refused an umbrella either).
If you go back 5-6 years if you looked at what Elixir was offering (EXP) versus D'addario was offering it would be easy to declare Elixir was better.
Fast forward today, Elixir is making the same strings and D'addario is on their 3rd version of their coated strings. EXP -> XT -> XS.
The guys at Taylor have probably been trying these all along (like I have) and came to their own decision. But they are also probably making the decision based on factors we don't care about. Like which one is more reliable at delivering container trucks full of strings on schedule, or which one has the best price on 100,000 sets of strings.
If Taylor wants to do D'addario because they get a better discount on 100k sets of strings that's obviously not relevant to us but it's fine for them to use that as part of their decision. But it's also legitimate if they just think the strings are better or suit a larger % of the Taylor lineup.
I kind of think Elixirs were a decent match with the brightest Taylor models.. but in recent years Taylor seems like they have released more and more guitars with a warmer voice, and maybe D'addario suits those better, but they don't want to worry about 2 suppliers.
I am also not sure what the chemicals are in the XS strings.. but Gore has said most of their stuff needs to go away, so Elixir strings may actually go away due to environmental concerns. If D'addario found a way to get the job done with less harmful chemicals that could be part of what's going on too.
I am going to miss Gore-Tex a lot more than Elixir strings if they both have to go away.