It's a "rule" added to the starport construction guidelines so that they didn't need to write rules for lots of different tech levels.
"Most SPA Starports have full access to TL 12 (or higher) equipment and facilities: they are either based on worlds with a sufficient level of technological development or TL 12 items can be sourced elsewhere and transported to the planet. This allows these ports to make use of all of the Modules presented in this chapter."
Except highguard 2022 specifically says this is not true.
“
SHIPYARD
The smallest shipyards are found on civilian stations for the construction of small craft but far larger construction sites can be found on the stations of megacorporations and militaries. Shipyards provide the facilities needed to build ships to the Tech Level of the space station.
A shipyard consumes two tons for every ton of the largest ship it is capable of building or the total tonnage of ships it can build at any one time (so, a 10,000-ton shipyard can build ships totalling up to 5,000 tons). For every ton they consume, shipyards cost MCr0.5 and require 1 Power. They also need one crewman for every 10 tons.
In order to construct ships with jump drives, a shipyard must be of a suitable Tech Level, as defined on the Jump Potential table on page 16. So, for example, to build jump-3 ships, a shipyard must be at least Tech Level 12. Shipyards capable of building ships with jump drives have their cost increased to MCr0.75 per ton.
STARPORTS
It is possible for a space station to be classed as a starport for a system. This can be either as a highport servicing ships that cannot reasonably reach planetside facilities or as the sole starport within a system. The class of starport a space station can be rated as depends on the facilities it can offer, as shown on the Starports table. All the facilities listed are minimums the starport must have installed.
Note that while a space station might qualify as a
starport by having the right facilities, that does not necessarily mean it is classified as one. Commercial pressures might force the designated starport to be elsewhere in the system or the local government might forbid a space station from being used for this purpose.”
Highguard 2022 pg 68. Your using 1ed rules that have been specifically replaced