This is a fairly recent change in behaviour:
If you move pages on iswiki, the old cached page title is displayed both on the article and the article's talk page until the page is manually purged. This happens on the Icelandic Wikipedida, but not on the English Wikipedia.

Steps to reproduce:

• Create the page https://is.wikipedia.org/wiki/Special:MyPage/test
• Move it to https://is.wikipedia.org/wiki/Special:MyPage/test2
• The title displayed will be "test" and not "test2"