The part number for A10 pistons is the same for the two different engines. [Coupe & Non Coupe] It's the cylinder heads that vary with one number for the Coupe & another for Non Coupe, so this must be where the extra half point of compression comes from.

Dimentionally, A10 & 1200 pistons are interchangeable, however the 1200 ones have a dish. With the extra 11mm of stroke the compression went up too much, so a dish was included to bring it down to the same as the KB10 engine.

Using flat top A10 pistons will restore the compression that was lost by the inclusion of the dish, but, depending on the source of the pistons [genuine or replacement], just be sure that there is no problem with the skirt to crankshaft clearance. I think that genuine pistons have a longer skirt.