Ryadia,
Yup you are correct while the standard parallel port on a PC is very well defined, and there are certain pins that are dedicated inputs and others that are dedicated outputs, the way they get assigned by various CNC products is all over the place. Each of these new Chinese versions decided to do their own assignments which is not an issue if you actually are provided the assignments but like you said the documentation on most of their products is lacking. Several people have taken notice of the Masso product, but it is not the only standalone controller that does not require a PC. See the link below for a Chinese version that does not need a monitor or keyboard, just a USB stick with your gcode program.
Free Shipping CNC 3 Axis offline stand alone controller engraving CNC router | eBay
The nice think about the Masso was it supported a nice color monitor and on the surface their videos suggest a really nice product. Several other users have reported several issues on these machines, but over time they should get all the bugs ironed out and it will be nice to be free of a PC like you said.
Several other users have reported good luck with the Chinese 3/4 axis standalone controllers and said they actually work.
Russ