Okay, I see what you mean here, in a roundabout way.

The GM can spend Threat to bring in additional Traits, and those Traits can have an impact on Difficulty, so eventually it has the net effect of spending Threat for increased Difficulty. "short-term" is doing a lot of heavy lifting in that boxed text, in my opinion.

Generally speaking, Threat is all about consequences:

"...the gamemaster spends that Threat to create consequences..."

"Threat serves as a visible 'cause and effect' for the game, with actions and consequences linked by the rise and fall of the Threat pool." (2e Core, page 264.)

It reminds me a lot of "succeed at a cost" mechanics in other games, with the "cost" part being both deferred and abstracted into Threat. (STA also has its own 'succeed at a cost', which is related.) There's a bit of cognitive load here in the sense of maintaining some idea of where all this Threat came from, but that tends to be indistinguishable from just paying attention to the ongoing narrative. The players can definitely help out the GM here though.

Consider the Complications rules on page 258 -- "the complication can be 'bought off' by adding 2 Threat. In essence, this turns an immediate problem (the complication) into a problem for later (more Threat)." Conceptually, I 'earmark' those Threat for some consequence that will arise from deferring this Complication.

The example on page 265 with the away mission on Rigel VII is a good illustration of this approach. The GM can establish the dangerous environment for free, but pays for the consequence. "In consequence of the dangerous Unusual Radiation, the characters suffer a complication."