Have you tried printing a single script in 13 to see if that works?
In that case, there is a noticible delay before the print dialog appears (there is no delay in 12), but the delay is not long enough go cause a pinwheel.
The length of the delay seems to depend on the length of the script being printed (or on the total lengths, if multiple scripts).
I just ran a test selecting a whole file of scripts and printing to PDF. I agree there is a delay, but not altogether surprising as there are a lot of scripts. There were a couple of differences: the FM13 document was 476 pages, and the pages were numbered; the FM12 document was 469 pages, and page numbering did not work (each carries page no -0-). The 7-page difference appears to be font related—FM12 printed in Helvetica, FM13 in Arial. No big deal it seems to me.
Interesting; you were printing about 9 times as many pages of scripts as I was and seem to have had less of a delay. So there may be something else going on that makes it worse for me.
Page numbering works in 12 for me. The difference is that when printing multiple scripts, 12 numbers the pages for each script seperately but 13 numbers them all consecutively.