Nothing about the chair seat & back dimensions has been altered from day one. The decision was made by Vertagear to change the seating of the gas lift in order for the chairs to appeal to a wider range of people with regards to height.
I've had a reply from Vertigear. they have made the chair suitable for smaller people:
Thank you for reaching out to us! You received the new version of the gas lift - which corrects an issue that was caused by the overall height adjustment of the chair. The original gas lift was for audiences from 1.75m to 2.00m but with the new versions are made for audiences from 1.65m to 1.90m. We wanted to make the chairs available to the average consumers which are 1.65-1.75cm to sit and tilt comfortably, therefore we decided to upgrade the gas lift. The gas lift cover is not compatible with the new version of the gas lift. Please let us know if you have any additional questions or concerns.
So basically they had an issue with the casting fracturing so bodged a replacement so there is now no room for the gas lift cover, & if you drop the chair whilst sitting you can smash the tilt knob if it's over one of the wheel struts
Now I've had the chair for a few hours I can see I will never be comfortable, the seat part is just 360mm, that's just 60mm wider than my kids old carseat !!. 5 minutes & my thighs ache as does the wifes, only my 8 stone beanpole son can sit comfortably, metal inside the thighpads is the cause as there is no give. right now I'm sitting on a cushion