the first time we harvested flow frames there was a largish leak of honey- it flowed out of the front entrance and pooled on the coreflute. We heard the queen bee piping inside the hive- she was not amused. Many bees bearded out the front- and they were flecked with honey. they set about cleaning each other and licking up the honey on the landing board- within an hour they had everything under control. We didn’t see any dead bees. I documented that here:
By contrast I harvested 4 traditional frames last autumn - after I was done I put the stickies in a Nuc box and put it in front of a hive to let the bees clean them up. As I did a poor job at spinning some remaining honey dripped out of the stickies onto the nuc box floor- the next day I was saddened to see about 150 bees had got caught up in it and drowned. I won’t make that mistake again. I have rescued bees that are buried in honey- and been surprised how readily they recover even when they were seemingly drowned good and proper- but if they struggle for too long they give up the ghost 
Edit: and this reminds me- from what I recall Flow says you should have the coreflute int he top slot when you harvest so the bees can lick up the honey through the screen if there are leaks: I disagree with this approach: if the pools are big enough the bees could drown in them. I either put the coreflute in the bottom slot- or remove it and put a tray under the hive. That way if honey leaks it flows right through the screen and there is no chance bees can drown in it. Afterwards I put the coreflute in front of the hive so the bees can clean it up- though- the last few harvests I have made there has been ZERO honey on the coreflute and no signs of leaks.