Strong non-lemma forms

It's not unique, it's shared by all past-tense forms. The practice on Wiktionary is to include the etymology for all forms on the lemma entry. In fact, non-lemma entries are kept as minimal as possible.

This practice doesn't seem to be the best approach for arbitrary, memorized strong forms like these. It is understandable for forms like "walked" to leave the etymology to "walk", but in the cases of forms like "brought", "did", "sang", where the etymology of the particular form can be independently traced back to earlier forms, this information should be more readily accessible from and noted in the non-lemma form's page.

It should be noted in the lemma form's page, as on *dōną.

Why? There is no reason for this. Each of these non-lemma forms have received individual attention from linguists through the last two centuries. They need to have this information on their own pages.

Non-lemma pages are kept as minimal as possible. Etymological information is consolidated on the lemma page. This is the standard practice for cases where a lemma has multiple distinct origins. Compare koelen, durven.

Are these not weak verbs? There is no form to memorize, they are regularly derived. This is in contrast to the case with the forms I mentioned.

Strong verbs are also regularly derived.

Even so, here's some suppletive verbs for your comparing: go, be, zijn.