It's a critical deviation, which shouldn't have been done on a whim.
Seldon's psycohistory predicted the path of the whole empire with great accuracy, but knowing their destiny would make people act differently, so Terminus didn't have psycohistorians, just a vault that would open at crucial events and give information. It would have worked well until the Mule threw a wrench with its mental ability to tune other minds. He wasn't a clairvoyant, he just altered people's feelings. The Second Foundation put the plan back on track thanks to their own mental abilities, but they also weren't clairvoyants. So far only psychohistory could predict the future. Later we have Golan Trevize, who also couldn't see the future, but had a gift for choosing right with incomplete information. Even Gaia had to rely on Trevize for its final decision.
Foundation's Gaal can see the future, and this is a world breaking ability. Hari Seldon and his psycohistory become obsolete since she can do that on her own, any action against the Foundation is moot, any deviation from the plan can be predicted, etc.
The only way to write Gaal out of that corner is making her clairvoyance work as reliable or unreliable as the plot needs (lazy writing), and judging from how she can predict and block micrometeorites now (which can puncture a ship's shield and hull, but not a tablet), it seems that's the route they will take. There was no need to introduce clairvoyance in the Foundation's universe.
I think there's a wide gulf between predicting the entire course of the collapse of a galactic empire centuries out into the future, and being able to anticipate a meteorite impact fractions of a second into the future. At most, Gaal has had a vague, bad feeling about something minutes before it happened. While they may have the second foundation refine this ability and be able to predict things out over longer time frames, as of yet there is no one who can make predictions in any way comparable to psychohistory. Whether or not there is a need for this really depends on where the story is going, which is at this point unclear but definitely not the direction of the original books.
The show seems to be heavily leaning towards the idea that this capability is going very important to the plot. A significant portion of the last episode consists of Hari Seldon explaining to Gaal how significant her powers are, and demonstrating that they can clearly predict complicated near-future events. I hope you’re right that the show will place tight restrictions on this macguffin, but I’m definitely worried.
Nothing that's happened in the show thusfar undermines the premise of psychohistory. Psychohistory is about using mathematics to predict the large scale and long term behaviour of society, it has nothing to do with someone having essentially heightened reflexes.
