Only two tackles projected to go in the first 50 picks, Christian Darrisaw and Alex Leatherwood, measured in last month with at least 34” arms.
Sewell is 33 1/4". 33" is generally considered the cut off. Rashawn Slater came in at 33" and some thought he might be the first tackle taken. Dillon Radunz was also about 33 1/4" and I think he going to be a steal in the 3rd (even late 2nd) if he makes it that far.
I'd say 3/4" in a OT's arm length is less of a concern than 30-40 pounds in a WR. TBH neither concerns me as both have shown to be worth a top pick.