The plum line from knee to pedal spindle is bang on.
This is a rule of thumb that originated in an era when we were a lot less empirically-minded. The notion that your stem should just block the front hub is another such rule of thumb. Funny enough, the rule that your max HR is 220 minus your age is an empirically-based rule of thumb - and really it should be described as the average max HR for a given age is 220 - age.
Rules of thumb may be correct or close to correct for the average cyclist. But they may not be exactly correct for you. For example, the average person my age should have a max HR of 178. I have observed 187 bpm during ramp tests, which means my actual max HR is probably a bit higher. Either way, that's a prediction error of at least 9 bpm.
Back to the original question, I personally prefer a much more forward saddle position than average. On the hoods, I can just see my front hub. The OP should make of this what they will. The OP also sounds like they are a bit uncertain about their bike fit. This is pretty normal, and this is also a good time to try to find a good bike fitter.
Bike fits given in the store are not what I'm talking about. Sales staff can get you very roughly in the right position, using gross rules of thumb like knee over pedal spindle. However, as I and others have discussed, we all vary a lot in our specific dimensions and preferences. Thus, serious cyclists probably benefit from seeking a good bike fitter. Moreover, our bodies and preferences change over time, so you so often have to repeat the fit sessions. It's true that this can be expensive, but if you are serious about cycling, I feel that it is a good investment - if nothing else, to be comfortable on the bike.