the title is on the tin. as tested by me and Kung, the 3-point and desktop IK uses the previous position as the origin of transition animations during locomotion.
This happens on both AV2 and AV3 avatars, on the Beta IK, not legacy.
Video of it happening
Relevant Discord conversation in the IK 2.0 beta channel https://discord.com/channels/189511567539306508/946881839400882196/966616634406105119