I mean, Thats true but Zoro bros has been on a streak lately
The perfect example of that is a majority of Z base, including myself going hey Zoro Vs King all the way it makes too much sense, most people were also among the lines of ZKK is silly since Zoro going up against a main character in a major fight is usually not Oda's pattern.
In reality the context was there the whole time, but a lot of people including myself ignored it.
In terms of Sanji the 2 main contextual points we have right now in terms of hints towards his fight is
SvK (skirmish, buttttt the personal beef is with Momonosuke) in 999 King made it a major point of executing Momo. In previous chapters he asked his underlings to bring Momo, With them Busy, King might take that into his hands and try to do it personally. That is where and why Sanji would intercept and fight King
SvQ (Queen brought up Vinsmokes, contexually a personally issue in the past could arise between Queen and Judge, that makes Sanji angry in some sort of fashion) They rely on technology buttttt no personal beef at the moment. Queen is not targeting anyone specifically at this point Sanji has a connection to (i.e scabbards and momo)
SvJ (Wait for context to see A. Where Jack is and B. his dialogue in regards to the scabbards)
For extra for this spoiler (Yamato has been spotted need to see that dialogue to see who goes after Yamato because Momonosuke is with Yamato at the moment as well and surely that will be announced and that leads to another direction Sanji could head towards)