Speaking as someone who has done contest prep diets for bodybuilders and regular folk.... there is huge individual variation in metabolic rate, and the existing calculators out there are all garbage at judging metabolic expenditure.
the only accurate way to determine your caloric maintenance would be to track your food intake while you remain weight stable, and then substitute that with an isocaloric amount of soylent.
They seem to gloss over this and blanket recommend 2000 cals per day