The problem with the superscraper is this: It will not scrape any yellow glue. If the yellow glue is gooey and sticky, pieces of tile are going to stick all over the floor, making cleaning the floor a little more difficult. We take the dust from our shotblaster and sweep it around on the yellow glue and it takes the tackiness out of it.
The straight blade scraper will eliminate alot of that.
I would not agree to 70% of glue removal. I would say all or as much as comes up with tile. I think it is hard to qualify 70% of glue removal.
If you get them to agree to all, then shotblast the floor.