I think it's a matter of semantics or maybe marketing.
It seems that lately, just about everybody refers to a stepper motor with an attached lead screw as a linear actuator. Techically it does what a linear actuator does, moves a component in a straight line, but that's not how a real linear actuator works.
In a true linear actuator, the motor and the movable platform are integrated. The rod, or more likely the rail it traves on, is stationary, and the traveling block has the stepper motor and rollers inside it.
This first video shows how a lead screw actuator works, and yes they call it a linear actuator.
https://youtu.be/uewMphsBamk
But this video shows a true linear actuator.
https://youtu.be/-dMKXUPLMW0
While they both do the same thing, the linear actuator is more complex and costs more. Hope this helps
To print or, 3D print, that is the question...
SD3 printer w/too many mods, Printrbot Simple Maker Ed., FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.