Is this what they call a pickup line?

Well people do say that the magnetic attraction that the pickups have on the strings can reduce sustain. Ergo, more pickups = less sustain. Whether that effect would be noticeable is debatable.

I have to say my first response to the pic was: “how much hum would a humbucker buck if a humbucker could buck hum?”.

Edit: a word

When I bought my tele the pickups were way too high. The stronger magnetic field killed the sustain on thickers strings and actually affected the frequency produced on the higher frets. I would assume that a wall of pickups would have a similar negative effects.

So, a pickup creates a magnetic pull on the strings, and this does have an effect on the way the strings are vibrating. It's an experiment you can do yourself: You can adjust the height of the pickup so that it gets closer to the strings. If it's close enough, you will hear a vibrato-effect when you're playing. Well, that's undesirable, unless you want to have vibrato everywhere.

So, if there's more magnetic pull on the strings, there's a higher possibility for unwanted vibrato; this could mean that you need to adjust the height, so that the pickups are lower (further away from the strings). Lower means a weaker signal/output; and the different strings might be affected differently, so this means different tone overall.