I think this caution section can be improved a lot.
It does not state if these 2 sentences are correct examples of using ものの or unnatural examples.
It would be more instructive to include some unnatural examples, clearly mark them as such, and show how to change them to be natural.
It’s a real shame, because this condition “topic or subject have to be the same” seems to be much more nuanced than these words imply.
For example, BP’s second test sentence:
工夫してみたものの、結果は大して変わらない。
It seems that both grammatical topic and subject are different between first and second halves, but the sentence sounds fine nevertheless.
The article as a whole is also missing information from DoAJG regarding questions/commands in the second part of ものの sentences.