Hi Pete and
to the site. You've done the right thing first and asked the right questions.
The short answer is that if a scopes tube is much shorter than its stated focal length then there has been something added to alter the light path. What is usually added is a cheap plastic (mostly, but whether its glass or plastic its not usually of good quality) barlow type arrangement in the focuser. These usually degrade the quality of the view substantially. Also the mount that these things come on are not called Wobbletronics for nothing. Mind letting us know what sort of price these things sell for? You can by a good quality 8" dobsonian for probably around $300 that would leave the 127 for dead