I do think Aziraphale's looking for rules -- just rules aren't the only things he's looking for, and he finds many other things he likes about books in his ongoing search for rules. He doesn't just collect etiquette manuals, after all. (N.b. that's my headcanon; we have zero onscreen evidence that Zira has a thing for etiquette manuals. That's not what Mrs. Beeton is, though that book certainly does have a lot to say about etiquette).
Eh, preview of part 4, why not: it's not so much that Aziraphale and Crowley and Muriel think everything they read is a rule, it's that they have this habit of reformulating everything they read as rules, because they're so damn desperate to understand how things work, and to have reliable guidance in dealing with their world. How relatable of them, right?
Jimbriel, actually, figures in here despite his functional illiteracy. He verbalizes every discovery he makes about how the world works, and every instruction he is given about how to deal with it! He's sense-making in real time!
So we get vavoom, and we get "it takes a few days because that's how it works" and we get the ball, and we get "but they're always such a little ray of SUNSHINE!" (note, of course, that Beez has already broken this so-called rule, unbeknownst to Crowley).
They can definitely look for rules in books, test rules, try haltingly to express rules... without ever arriving at The Rules. Kinda what most of us do, really.