Gotta be something that I am doing wrong

Bill used to recommend a brass bridge because it wouldn't interfere with the pickup's noise cancellation.

I think it's something to do with the magnetic bridge plate interacting with the top coil's field, but not the bottom coil's. As I understand, side by side designs don't have the same issue.

 

Yes. Even when both coils are perfectly identical in number of winds and magnetic Gauss, it's not 100% humbucking operation because the two coils are not occupying the same physical space. So there will always be some loss of humbucking capability. The same goes for stacked-coil humbuckers: one coil is closer to the strings than the other, so it's not perfect. But in practice it all works pretty well because it's...good enough.

Gibson-style humbuckers do "buck the hum" better than--for example--an RWRP Strat set when position 4 on the switch is selected. That is an even lesser degree of "partially" humbucking operation.

It all comes down to limitations created by physical characteristics of pickup construction that lead to varying degrees of humbucking operation.

Here's some cool hub-mucker trivia: nine-pin dual triode tubes, such as the 12A-7 series, have filaments wired for humbucking operation. So if you hate the sound of humbuckers, you better switch to an amp with octal preamp tubes

Cheers!

 

The type of metal in a Tele bridge can definitely affect the hum-canceling ability of a stacked humbucker. I replaced my Tele bridge plates with stainless steel versions, and it completely eliminated all trouble. Stainless steel is a much better choice than brass, both electrically and acoustically.

 

If you aren’t opposed to modern looks and want to save money, the standard modern/MIM fender bridge will eliminate this. OTOH with that stamped steel plate interfering with the hum cancellation also comes some microphonics - which IMHO adds mojo. On mine I can live with having a little bit of hum for that.

On the other hand, I’ve wondered if the same phenomenon occurs with split style (instead of stack) pickups.