Yes, you would lose the REVO infill above ground.
As an alternative you could export the separate TX8 and REVO 'above ground' clouds to CloudCompare (.e57 export from TRW), and run a Cloud to Cloud Distance computation.
You could then split the REVO cloud on the basis of distance from the TX8 cloud, I guess you'd have an idea that all REVO points greater than 'x' distance from the TX8 cloud would be required as infill. The split cloud could then be saved as .e57 again and reimported to TRW.
Still a bit of manual intervention/processing to do, but less than trying to identify and delete overlap in the project cloud.