Paramount+, which is arguably an authoritative source on this, lists Caretaker as a two-parter (1x01 and 1x02), for 16 episodes in season 1 overall.
Wikipedia lists Caretaker with two episodes, with a note
Originally shown as a two-hour pilot movie on the UPN network, but in syndication is shown as two separate episodes.
Here’s the curious thing, though: Caretaker’s Production Code is listed as “101 and 102”, with 103 for Parallax and 116 for Learning Curve.
So terms of production, it was clearly treated like a two-parter.
Wikipedia has one page for Caretaker, but in the season 1 episode footer lists part 1 and part 2 - both leading to the same page.
The DVD sets seem to have 15 episodes, with Caretaker as one episode.
IMDB also has 15 episodes, Caretaker as one.
Memory Alpha describes the production process in detail and it’s clear Caretaker was filmed as one pilot.
So basically, both approaches are correct in some way: It’s one episode in the prime run and on DVD and by the way it was produced, it’s two episodes in syndication and on Paramount+, and it occupies two production codes.
So it’s really a classic matter of idealism vs. realism, prescriptivism vs. descriptivism: Do you want Trakt to match the ideal of the season, as it was broadcast 30 years ago, or do you want it to match the reality of the season, the way it is broadcast now?
Considering that the point of Trakt is to track what you watch, sticking with Caretaker as two episodes is the functionally better choice, because it allows those watching Voyager from primary sources today to track it as they watch it.
In addition, the “watch now” button isn’t really going to work if the organization of the season doesn’t match the way it’s actually organized in the world.
If you link people to watch 1x02 Parallax, but they end up at 1x02 Caretaker, Pt.2, that’s not helpful to them.
Moreso, Caretaker as two parts is the way it already is, so if that were a terrible solution, it would already have shown.
Going the other way would require a lot of shifting, dropping of data, etc., only to bring Trakt in line with a way of showing the episode that hasn’t happened for decades.
I understand the desire to reach the ideal and to achieve synchronicity with other services, but changing the way VOY is organized purely for synchronization’s sake comes with lots of drawbacks when it comes to the primary function of Trakt: The actual tracking.
I don’t think it’s worth it.
Especially since the production codes show that the whole “they are 15 episodes” position isn’t as clear-cut as one would think.