Tallit & tefilin just before baruch sheamar

Hello
What is the reason behind the german minhag of putting tallit gadol and tefilin just before baruch sheamar and not at the beginning of the tefila before birkos hashachar (as it is the custom of many other ashkenazim) ?
I read in Rav Shwab Iyun Tefila that it was because in germany it was very common to start the tefila before misheyakir so they put talit and tefilin later but he add that in shabbos, as we start tefila in a later time than on week, we put the talit at the beginning before adom olam (but I remark that it is not the minhag of my local yekka shul)
So if we follow this demonstration we should put talit & tefilin at the begining of the tefila each time we start before misheyakir (but again it is not yekke minhag)
Why so ?
Many thanks

Since the minhog is that the chazzan says the brochos out loud on tallis and tefillin and it is a part of davening - seder hatefillo so we want to keep it consistent. However, in other shuls the chazzan goes to the omud already wearing tallis and tefillin it is merely something he does as a private individual, so he puts it on before davening unless it's too early. This is my understanding of how we do it in Washington Heights.

already answered : www.kayj.net/forum/minhogim/143-the-time...nd-taken-off?lang=en