That’s like making a blanket issur on chicken because there was a tragic incident where one store brought in treife chickens. How does anyone here truly know that that’s how almost all retzuos are made? I grant that there are some that are indeed posul. Did the quoted poskim address this as a “Most retzuos are possul” issue, or were they responding to specific shailos?
As with all such public proclamations, buyer beware. It is important to raise the issue for public awareness. But the sounding of an alarm is more often not warranted. Essentially, it brands most sofrim as well as stores that sell tefillin as dishonest and machshilei es horabim. Can anyone here provide evidence and warnings from the Gedolei Haposkim that substantiates this call for alarm?