It's been in the game since 2014, but it didn't apply
to core gems until January.
Here's an example from 2018 of it applying to Coffee
(Coffee is a particularly hard-hit good for it, for some reason - whoever sold then lost about 400 credits/tonne on the sale, which would be about half their profit)
Of course, no-one cared about it applying to Coffee, so it's only since January that people have complained about it.
It added supply and demand - and therefore made bulk tax apply because the price at 0 demand and the price at full demand were no longer the same - but it also added an infinite demand regeneration rate rather than the "takes about a year to refill" a good with that galactic average price might be expected to have.
Then - not in the patch notes - this month's release gave the same infinite demand regeneration rate to the other core gems. Presumably to make them more competitive with LTDs, and because the general player response to any supply/demand mechanics that matter has been overwhelmingly negative.