The split aileron is indeed (much) less susceptible to adverse yaw. It is also much less efficient at producimg roll: around half the rolling moment has disappeared, due to there being no downwards pointing aileron.

Above pic from prof. Gerlach’s uni book was first used in this answer: the right hand side of the graph shows the additional cl*c from a downwards deflected aileron, which disappears when using the split one.

As stated in @Mark’s answer, the later versions B-52 had replaced its small ailerons with spoilerons. Not for reducing adverse yaw, but for eliminating aileron reversion. From the wiki:

Because of the B-52's mission parameters, only modest maneuvers would be required with no need for spin recovery.

B-52s prior to the G models had very small ailerons with a short span that was approximately equal to their chord. These "feeler ailerons" were used to provide feedback forces to the pilot's control yoke and to fine tune the roll axes during delicate maneuvers such as aerial refueling.[102] Due to twisting of the thin main wing, conventional outboard flap type ailerons would lose authority and therefore could not be used. In other words, aileron activation would cause the wing to twist, undermining roll control. Six spoilerons on each wing are responsible for the majority of roll control. The late B-52G models eliminated the ailerons altogether and added an extra spoileron to each wing.[102] Partly because of the lack of ailerons, the B-52G and H models were more susceptible to Dutch roll.

Present day high subsonic passenger jets mostly have two sets of ailerons, inboard and outboard, plus spoilerons. Inboard ailerons to be used at high speeds, also to eliminate aileron reversion.

It is possible to produce a split aileron, which would indeed be(much) less susceptible to adverse yaw. But there are downsides as well:

• It would create complexity, and therefore higher risk of failure. Which is not wanted in the flight control surfaces, the input to controlled flight safety.
• It is also much less efficient at producing roll: a significant portion of the rolling moment has disappeared, due to the lower surface not contributing to the up flow diversion.

Image source

Above pic shows how adverse yaw is eliminated without adding complexity: the frisé aileron has a lower corner that pokes out when deflected upwards, thereby increasing drag.

As stated in @Mark’s answer, the later versions B-52 had replaced its small ailerons with spoilerons. Not for reducing adverse yaw, but for eliminating aileron reversion. From the wiki:

Because of the B-52's mission parameters, only modest maneuvers would be required with no need for spin recovery.

B-52s prior to the G models had very small ailerons with a short span that was approximately equal to their chord. These "feeler ailerons" were used to provide feedback forces to the pilot's control yoke and to fine tune the roll axes during delicate maneuvers such as aerial refueling.[102] Due to twisting of the thin main wing, conventional outboard flap type ailerons would lose authority and therefore could not be used. In other words, aileron activation would cause the wing to twist, undermining roll control. Six spoilerons on each wing are responsible for the majority of roll control. The late B-52G models eliminated the ailerons altogether and added an extra spoileron to each wing.[102] Partly because of the lack of ailerons, the B-52G and H models were more susceptible to Dutch roll.

Present day high subsonic passenger jets mostly have two sets of ailerons, inboard and outboard, plus spoilerons. Inboard ailerons to be used at high speeds, also to eliminate aileron reversion.