The "faction specific" tag on a normal tech usually means that it differs from the norm in some way.

For example, all the techs that normally allow planetary improvments (i.e. SPIN Network) are "faction specific" for the Vodyani, because they cannot use planetary improvements with their Arks. Since those techs don't give planetary improvements, they are not the same technologies other factions get, so the game considers them faction specific for the Vodyani.

Sometimes it's fairly small. IIRC the tech that increases the threshold for overcolonization disaproval has the faction specific tag for UE, because they get a bigger bonus: if you don't mouse over and look at what you get, you might think it's there for no reason.

IMO it's something I'd really like for the devs to try to find a clearer way to convey; knowing the difference between that tech and what's normal can help a bit in figuring out how it might fit in your plans better. Unless you have several games under your belt, you probably have very little idea why that non-ship technology that you've seen on other faction's tech tree is "unique" to them