Luan is a resinous wood----very often paint--varnish--glue--and thinset will not bond to it.
The best use for luan is to protect your finished floors while moving the appliances back into place.
I have used Luan for at least 25 years. Back in the day when it was 'really' Luan, too. Back in the day when you were on a budget and preferred spending $8 for a 1/4" sheet of Luan as opposed to $15 for a sheet of birch...
The quality of Luan or whatever seller is putting off as Luan has definitely gone down in the past 10 years. There are more voids and it has a much open grained feel to it. However, it is a pretty simple process to avoid contamination. Any number of products will do. Leading the list would be a wash coat of sanding sealer shellac. Or a white pigmented primer by Bins or Zinssers. Sadly, the gap in price between Luan and other sheet goods has closed. Anymore, its an adventure going to a box store in search of decent plywood.
I got a full-blow workout it plus several nasty slivers moving castoff sheets of 1/2" BC over to the next rack in order to cull out 9 decent sheets. Two of which the next morning had curled back so much, I thought anymore and they will touch end to end.
Anyway, the sub floor in the kitchen and bath are now layed down. On to the Ditra.