[Mesorah] Hypercorrections or adaptation?

[Richard]

R' David Cohen:
<<I think RYBS said "Shir haMaalos: miMaamakim" during 10  Yemei Teshuva, but
said it before Yishtabach, as part of pesukei deZimra. >>

FWIW Yekkes don't say it there at all.  I'm not sure if the issue is hefsek or something else.
-----------------------------------------
אמר ריש לקיש קשוט עצמך ואחר כך קשוט אחרים
בבא מציעא דף קז,ב
בבא בתרא דף ס,ב
Shalom, RRW