I heard someone speak about this in the Alumni Beis Medrash (adjacent to Beis Shalom of BMG Lakewood NJ)Two. Two of the points made were as follows
R’ Eliyashiv after hearing about this problem from R’ Shlomo Zalman Auerbach ( hishis mechutan) was makpid to that from the first kos to second kos be less than an hourhour; this way it definitely wouldn’t need a separate bracha achrona.
He asked this question to R’ Dovid Soleveichik, who answered,: you’re right, but a mesora is a mesora!! and that is what the Shulchan Aruch says to do.