The previous delivery also entered service within a day or two. I think that the pause in deliveries was caused by Angel Trains/ScotRail insisting that the refurbs were delivered ready for use. I seem to recall that some of the early units were quite unserviceable with roof leaks etc. And that Wabtec vans were observed at Haymarket, presumably with staff rectifying these faults.
Doesn't explain why so few refurbs are in use each day. Excluding one set at Brodies for a scheduled exam, they now have eight plus Classics.