Just telling you what my eyes see.
In more detail, here's what I saw on TV here in Montana, game-time. I don't pay for access to all-22's so bear with me.
Early on, he got boxed in by a DB and couldn't reach the ball. Twice. It looked like single coverage to me all the way but could have been handed off to safety, although I didn't see either play develop. Better route running, being able to fake and go on that DB might have had different results.
After that, I didn't see McVay call those 1:1 routes for Atwell, but instead broke him free on bunched sets where the routes by different receivers went all over the place, and Tutu broke free - just as (presumably) McVay drew them up. JY53 could probably draw it up and tell us exactly what happened. I can't do that - I only know what my eyes saw.
On those plays, Tutu came down with the ball, once I recall in traffic and took a heavy hit. I held my breath. Oof! He hung on.
Knowing where to go is part of route running. Tutu has obviously improved on that part since last season.
How you get there - that's another part. Kupp is as good at that part as anyone I've seen in over fifty years of seriously watching NFL football - possibly better. I could see Kupp-like moves from Puka as he got off the line yesterday. Kupp has moves that can leave a DB standing in his sox at the line (or falling on his butt in the endzone) and Puka has picked some up, already.
If Tutu could have put a shake on the DB covering him down the left sideline during yesterday's game and gained half-a-step instead of trailing behind the DB's left shoulder, he'd have had at least a chunk on one play, maybe a TD on the other. Open grass in front of him, ball on target...
That's what I mean by improving his route running.
When he does that - remember how Brandin Cooks used to get free going long 1:1?
I hope Tutu can work with Kupp more through the season, now that camp's over. He's already learned a lot from his coaches, and presumably from Kupp. When it all comes to fruitiion he could be a freeze-dried version of Tyreek Hill - who has the speed AND the route-running moves.
Thanks for asking. Always good.