1man: Ashkenazim also don’t say BHUB in magen avos on Shabbos… because it is a hefsek and one must not speak out till after kaddish tiskabel/kaddish sholem as stated in Sh.A.
Likewise one cannot answer it during psukei d’zimra because it is not a “complete” obligation – per Igros Moshe O.Ch 2, s. 98; Yabia Omer vol 2, s. .