Hi @maque4004,
Unfortunately I don't have a good answer for your question here as this is a rather unexpected behavior (as explained by the ANCOM developers in that link). It is likely an error of the test under some tricky conditions. The results from your non-corrected test seem reasonable (i.e. high W features are typically the truly significant ones) but of course without accounting for multiple-testing you significantly increase the rate of false positives.
The second scenario where low W values are considered significant is obviously unreliable and so shouldn't be trusted (as explained in the other link). My recommendations are to try a different tool for your differential abundance testing, example: q2-aldex2, q2-songbird, or q2-conrcob.
p.s I've moved this thread to "Other Bioinformatics Tools" as it wasn't directly using any Qiime2 tools.