Regarding OP's link to a no-name plug, I think it's mostly marketing. Solid wiring is often used in building wiring. See John Gardeniers answer regarding stranded / solid wiring these should use different plugs.This is to minimize crosstalk and noise near the plug (where the cable is un-twisted, and much more susceptible to interference). Many cabling systems now use a little 'form' to hold the wires in place before the plug. More and more manufacturers are updating their cabling systems, both to allow faster cabling work, and to ensure more consistent and/or higher quality.If the wires are thicker, the plugs are different. 23 gauge copper wiring (thicker wires) is more common in Cat6 installations than in Cat5 in my experience.Having said that, the following comes to mind: I would guess - but I'm not 100% sure - that the standards are mainly concerned with externally observable characteristics of the cabling such as crosstalk and attenuation, and leave the internal implementation details mostly up to each manufacturer. To the best of my knowledge, the standards themselves do not mandate any changes to the plugs.
