Is there a reason why this isn't "they caught the police", which seems more literal?
The prefix di- makes it passive. "Mereka menangkap polisi" = "They catch the police", "Mereka ditangkap [oleh] polisi" = "They are caught by the police." The "oleh" ("by") is optional, in Indonesian, you can just say "They are caught the police" and it'd make perfect sense, so it can be a bit confusing for an English speaker at first. ^,^
That terrible English articles... 50% of my mistakes are not made in the language which are being learned now. Like here: "By police" -- no, by THE police. Wrong answer! I know, that it is a real mistake, but... I'm learning Indonesian, not English :-( Maybe, these moments should be forgiven :-)
But you are choosing to learn it in an Indonesian through English program. The same thing happens to me when I do Catalan and Guarani. Spanish is far from my best language, unfortunately. Sometimes I will warm up by doing a bit of the Duolingo Spanish just to remind myself.
On the plus side you end up brushing up on your Spanish at the same time.
Absolutely. I honestly wish there were Occitan through French or Georgian through Russian or Sami through Swedish or any number of other things to help brush up on those languages.
why is it demanding tense specificity when there is non implied in the Indonesian clause?
I would think "are caught," "were caught," and "will be caught" should all be accepted. Of course, it is passive, which is constructed with the past participle in English.