u/Ivyyy1015

I moved a small site from /en/* URLs to root-level URLs about three months ago. I thought the migration was mostly settled until I exported the page report from GSC and actually added up the old URLs.
In the May 10–August 9 window, 97 retired /en/* URLs had 8,821 impressions and 25 clicks. The whole site had 9,986 impressions and 39 clicks. So the old URLs were still getting 88.3% of impressions and 64.1% of clicks.
One old URL by itself had 908 impressions and 20 clicks. That URL had not served content for months, but it accounted for just over half of all clicks on the site during the period.
I went back through the migration because my first assumption was that I had missed something obvious. The old URLs return direct 308s, with no chains. They are not blocked by robots.txt. The sitemap and internal links only contain the new URLs, the new pages are self-canonical, and there is no old hreflang setup left.
It was not a completely clean sweep. I found seven old URLs redirecting to destinations that now returned 404. That was my mistake, and I fixed those separately. They had about 58 impressions between them, so they do not explain what is happening with the other 90 URLs.
What confused me most was this:
• August 3 export: 7,279 impressions on old URLs (94.7%)
• August 11 export: 8,821 (88.3%)
• August 12 export: 9,028 (86.1%)
These are rolling three-month exports, not identical date ranges, so I know this is not a clean comparison. But I had already looked at the falling percentage and told myself consolidation was improving. Then I noticed the absolute number was going up. Most of the percentage change came from new content increasing the site total.
The latest seven-day window I have, August 4–10, still shows 45 old URLs receiving 1,326 of 2,183 impressions.
My current suspicion is simply that many of the old URLs have not been recrawled often enough. I removed them from the sitemap and replaced every internal link during cleanup, which also means there are fewer current signals leading Googlebot back to them. That is only a theory, though. I cannot prove it from the performance report.
I also compared the eight old URLs with the most impressions with their new equivalents. Three new URLs have their own rows in GSC. Five are completely absent from the page report.
I realize that an absent GSC row does not mean zero impressions because of reporting thresholds. Still, I cannot find anything that separates the three that appear from the five that do not. It is not publish date, position, or whether the slug changed.
If you have handled a similar path migration on a small site, did you see both versions reporting for a while? Or did the new URL only begin appearing after the old one dropped out? I am trying to work out whether those five missing new URLs are a normal in-between state or whether I have overlooked another signal.