Maybe. If Washington had done the 3cone his RAS score would have been lower than Gronk's. Washington has a great short shuttle (I think you implying that) which is an indication of lateral quickness, which I do not care about for a TE. Look at Gronk's short shuttle, which is atrocious, but TEs run seams and outs, rarely does a TE stop and move laterally IMO. Washington skipped the 3cone which measures the combination of quickness and flexibility, sometimes called agility. Washington skipped it because he is either not quick or not flexible or both. His 10 yard split is above average, average for most skill positions, but above average for a TE (larger, strong, heavy guys). Gronk's 10 yard is great.
So Gronk has great acceleration, Washington has good acceleration. Washington can't jump, Gronk can. Washington has great lateral quickness, Gronk doesn't. And we assume Gronk is more flexible since he took the 3cone. Watching tape it looks to me that Washington is a bit slow off the line so I said lacks "quickness". Maybe I should have said "explosion" since he can't jump. All of these drills blend together so it is tough to isolate any attribute.
Having said all that, this is all splitting hairs. Washington is a beast and will, IMO, be a good, maybe great, NFL player.