I didn't have a change of heart, I would neither glue straight on to a chipboard subfloor nor straight onto a thin screed layer on the chipboard.Glueing straight over a thin screed layer over chipboard? I wouldn't.
What's your reasoning for a change of heart?
The glue is between the underlay and the timber. The underlay sits unbonded on the surface. Can you tell me what is the difference between the underlay sitting on chipboard versus sitting on the screed that's bonded to the chipboard please?
Using Elastilon is quite a different matter: you don't glue the boards straight to the chipboard or the thin screed layer, the adhesive on the underlayment bonds the floorboards together.