THIS.
Your tech is wrong. Unless your neck pickup is RW/RP, the screw coil in the neck pickup is the same wind direction and polarity as the screw coil in the bridge pickup. Combining with the bridge slug coil will cancel hum, but it's NOT out of phase. I've had several of my guitars wired this way for years with zero phase issues.
EDIT: In terms of tonal change, it really doesn't sound noticeably different (other than hum-canceling) from splitting both pickups to the slug coil. If you're looking for a fatter sound with both split, add a switch to allow combining both pickups in series.