Yep. The two halves of the speaker present their 4 ohm load at different frequency ranges, and have a higher impedence outside of their active ranges.

The problem is that without an electronic crossover you're sending all of the frequencies to both amps anyways, so you wouldn't get the benefits of a "real" bi-amp system that sends different frequency ranges to each amplifier.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8