Just a thought! What if after each challenge it was repeated with the order reversed, The learner already somewhat proficient in the English to Welsh would then do a Welsh to English for the same phrases. Could this possibly be a helpful listening exercise?
I don’t know if this would be of any use, but you could try this exercise. It doesn’t promote active listening, but it does test understanding.
After you’ve finished one of the listening exercises (the ones where they speak at double or triple speed, not the normal challenges), download the Welsh version of the transcript and have a go at translating it into English. Then have a look at their English version and see how close you were .
The listening exercises are almost entirely based on vocabulary you already know (there are usually a couple of new words, but not many), so it’s a good test of understanding.
I did this for a while and found it really helpful. Of course, it’s still important to do the listening exercises in the way they’re meant to be done first!
HTH as a suggestion.