I think there was a correction in a digest magazine, it was certainly changed for COACC.
The MT errata document has this:
"Page 86, Top Vacuum Speed (correction and addition): For flying vehicles, especially those that can go outside the atmosphere, top vacuum speed has no real meaning. Other than the speed of light, there really is no such thing as “top speed” in a vacuum. The craft can accelerate as long as it wants, and can attain any speed desired—limited only by its duration and acceleration. Therefore, acceleration in Gs is a more sensible and useful number than top vacuum speed, since it tells you how quickly the craft can change its speed. Once you know the craft’s maximum acceleration rate, you can compute the travel time using the basic travel time formula found in the Referee’s Companion. Therefore, Top Vacuum Speed should be replaced by MaxAccel in craft profiles.
Top Speed applies to craft operating in a standard atmosphere only. Note that wheeled, tracked, and legged vehicles are subject to the same top speed restrictions as flying craft, based on their streamlining. For example, an unstreamlined wheeled vehicle can never exceed 300 kph in a standard atmosphere. If the wheeled vehicle needs to go faster, it must be streamlined, just as any flying vehicle."