Self-parking predates 2.5" drives. It was a highly-touted feature of some of the last MFM/RLL disks, so you would no longer need to remember to issue the DOS "Park" command before shutting off the computer. All IDE disks came with it since 1986, using a really clever mechanism--when power is cut, the momentum of the still rotating disc uses the motor as a generator to power the movement of the head arm to its parking area.
Of note, before SSDs became popular, many 2.5" drives had a "free-fall sensor" which would forcibly park a still-powered-on disk if a drop was detected, in time to prevent damage from a >8" fall. Such a thing would not help with direct impacts.