Kevin seems to imply that text is always meaningless unless written by a native speaker. Surely the existence of this website implies that there is hope for language learners, so there is a flaw in his reasoning. I am also more optimistic than he about being able to spot grammatical errors even without fully understanding the text in question. The language of the text is not brilliant, and it could be improved, but it is grammatically OK, and it is possible to compare the two options for grammatical correctness: 2 is correct, 1 is not. The difference between the two options is the preposition 'at', which is missing from option 1; if you added it, "When it is looked at" then 1 would be OK, but as it stands it is not.

Nothing here was written by a native speaker including the two choices, which renders the whole text meaningless.

I agree with Jimmy's approach. If the text was in a test, then I would be worried about the accuracy of the test because of the odd language. Nevertheless, the answer of the tester is correct in this case. You are struggling with a tricky area of English grammar, which is the need to avoid dangling participles e.g. While laughing a lot at me, I was very upset. In my silly example, we don't know who was laughing. However, in your sentence (Looking at it), there in an indirect object (it), which is clear. The sense of "look" is "consider". It's obvious from the whole context that it is a general point, and so the presumed subject is the general "we" "you" or "someone". Of course, this is a perfect context for a passive option too (when it is looked AT).

2) ‘Looking at it from their angle’ sounds fine to me. The ‘it’ is the training referred to in the previous sentence. The second sentence doesn’t connect very well with the first, but that makes no difference to the sense of option 2 in the gap. You could use 1) if you added an ‘at’ at the end, but option 2 is better, the use of the present continuous as in the first sentence carries forward better. Changing to ‘looked’ instead of ‘looking’ is a bit jarring, and ‘when it is looked at’ is a bit verbose when compared to ‘looking at it’.