Tag pages are updated as new posts are added, so frequently used tags have a higher chance of appearing at the top in searches. If you give the same title to the post and the tag, provided there are other posts with that tag, the tag will of course appear earlier. However, I don’t think it’s healthy for the same title to appear as both a post and a tag on your site. Neither from a user nor an SEO perspective.
Based on my WordPress experience, I can offer the following general advice: Construct your post titles and content primarily with SEO in mind; try to arrange categories, tags, and other menu layouts primarily from the user’s perspective, in the most useful way possible. Sometimes while focusing on SEO, we move the site away from functionality and user experience. This leads to dissatisfaction and lowers metrics such as time on site, return visits, etc., which can harm the site.