I find these questions entertaining. In general in the Litvish world specific halakhic questions are decided because the strength of the arguments, in conjunction with the Gadol who took achriyus for them.
So in regards to shaving, the fact that the chazon ish felt it is assur doesn’t make it assur. The heter of כעין תער as explained by Rav Moshe is compelling, and therefore accepted by the American poskim.
Now can we get an explanation why it’s ok to abrogate the prohibition of eating before shacharis?