They take the work elevator to near the top and then cross over on one of the anchor braces attached to the tower. Still some climbing but not 60 stories worth
If I had to guess- I'd say it was some combination of installing the facade support system on the upper levels (which seems to have been a bit more complex than the system below) and the recent inclination for poor weather.
Someone had asked what it looks like now from the pike/128 connector with the towers visible above the trees. It looks like this now, getting more substantial by the year. Winthrop ctr will add another, SST, and who knows what else maybe gcg office.