A bit ago, I went back and watched some closing minutes from the MIA series and I was struck that the Cs generally played JT/JB/Al/Smart/MB. A couple of times I think GW was in there instead of MB. But no White.White is playing 4 more mpg than last year (not nothing), but clearly Pritchard was the major recipient of swapping 2 guards (Smart/Brogdon) for 1 (Holiday). He's averaging 7 more mpg, which really doesn't show the whole picture since he had so many DNPs last year. It's more impactful to point out that he's already played more than twice as many minutes this year as last year (and unless I'm forgetting something, he was healthy all year).
I don't know if there's a way to see who was closing games last year, but IIRC White was in the closing lineup more often than not. Except for rare occasions, it was Smart/White/Brown/Tatum/Horford. Moving Smart and Brogdon didn't change much there, I don't think.
NBA.com lets you sort by quarter. It's not the closing lineups but it's a proxy. Here are the mpg in the 4Q for the Cs during last year's playoffs: