[bell-cot]

It doesn't need to be a fully accurate simulation, any more than your car needs a fully accurate ICE simulation to decide "Change the engine oil".

Just count accesses to each row, and refresh the adjacent row(s) when some limit is reached.

[inigyou]

Half-Double is an attack where you hammer the rows 2 spaces away so that the automatic refresh on the rows 1 space away is what actually hammers the target row.

[bell-cot]

Yes? When a given row's counter hits the limit, you refresh every other row which your actually-competent testing has shown might maybe possibly be compromised by that activity.

Same as a good car's computer doesn't make a bunch of rosy assumptions about whether the oil needs changing or not - the automotive engineers actually do their jobs, test the crap out of their engine designs, and base the oil-change criteria on the real-world test results.

(JIC: "Adjacent" has a range of meanings in English. Those go from "the singular closest neighbor, within further constraints on type, orientation, etc." to "relatively close to by some metric". But I am not an EE, let alone a chip architect, to know the "real insider" lingo here.)