Have you heard about the legend Fabrizio Romano? This Man doesn't lie when it comes to football and players transfers. So far as Fabrizio Romano has reported that this club has signed certain player, just believe it to be true. The reason why Arsenal haven't announced it yet is because the player have to pass his medicals and sign all necessary documents before he can be confirmed by the club. Viktor Gyökeres transfer to Arsenal has passed the stage of "here we go" so technically he is already an Arsenal player and I believe the club will announce him in the next few days.
I know that Fabrizio has announced that Gyokeres deal is done. But he had sometimes made mistakes of announcing that a player had arrived to a club on medical and later that day another
club steal a player right in front of their nose. Im a little sceptic I might say about it because Im a Arsenal fan so I would like the transfer to be over ASAP and see a video on Arsenal News

.
How many time has something like this happened with Fabrizio's news? If something happened once in 5 years or more, we can't question the integrity of the Man. So to me he's still accurate with his news. And in this case Viktor Gyökeres made it clear to Manchester United that wanted to snatch him in the late hour that he only wanted Arsenal and Fabrizio said it's a done deal, so you Arsenal fans should chill your Viktor Gyökeres is already in the bag for your club. There's no need for you guys to panic nobody is hijacking this deal at this stage.