You're confusing active/passive biamping with vertical and horizontal biamping. Easy to do!
I would do a search on the net or the asylum for "passive active biamping" and "vertical horizontal biamping" and you'll probably get more info than you need.
Quick primer: active biamping uses an outboard crossover system between the pre and amp(s) to send only certain frequencies to certain drivers. Passive biamping uses multiple amps to send full signal to certain speaker drivers. People futz with combining ss and tube amps to different drivers...
Two kinds of Passive biamping: Vertical/Horizontal
For vertical, think of an imaginary line drawn down the middle of the system; the right amp sends it's two channels to the right speaker's two inputs (or 3 channels to three inputs, etc.). In Horizontal biamping, put the imaginary line through the middle of the amps; half of the two amps' channels goes to bass on both speakers, the other half goes to treble on both speakers.
I have not tried active biapming, but many rave about it. I have tried vertical as well as horizontal passive biamping. Over the years, I have found that moving to a more powerful, refined amp has been of more improvement than chasing biamping passively. FYI, I have also found that a higher end, more refined speaker with only one set of inputs (single wired) can sound far better than many lesser biwirable/biampable speakers.
Finally, it is well worth time to consider monobloc operation. I feel I have close to the ultimate setup in terms of simplicity and power by using twin tube hybrid integrated amps in bridged/monobloc mode. This has yielded the best sound for me. I am surprised more people do not do so.