I think the different model numbers are there because one is resold by Amazon and one is direct from Weber via the Amazon website. No difference in the actual grills other than one was probably manufactured in a different calendar year so has a different date code. Mechanically I haven't heard that Weber upgraded the OTG in any way. Amazon probably just has units manufactured last year still in their warehouse.
~ Scott ~
Blue Weber Performer + Craycort CI • Brick Red Weber One-Touch Platinum • Weber 26.75 Kettle • Akorn Kamado • ET 732 • Record-crushing ORANGE Thermapen • UDS In Progress