They aren't the only team interested in him though. Bayern Munich is also after him. But just as it says in the source, Nico prioritizies Barcelona. He probably wants to play side by side with Yamal as well. 
It is true that Nico Williams has prioritized Barcelona, but i hope the club has the financial capacity to sign him, and not just that, i hope they wouldn't have problems registering him, as well as Joan Garcia they signed from Espanyol. Remember what happened last season with Dani Olmo, it was somewhat embarrassing when they couldn't get him registered, though they eventually did, i hope they would not have such challenges this time around.Nico Williams have shown interest in Barcelona which I believe it's the influence of Yamal but if Barcelona can't make it happen then he will be going to Bayern Munich or any other club that finalize the deal.
It's really embarrassing for a club like Barcelona to sign players and not be able to register them, I believe they would have things sorted out by now and won't be like last time.