Do the /sit macro and/or mashing the X button work for the purposes of Paladin Reckoning? How?

Reckoning is a Paladin’s ability in Classic/Vanilla World of Warcraft (1.13/1.12). When fully leveled, after being subject to a critical hit, the user gets a “reckoning stack”, becoming entitled to an extra attack against the opponent when the Paladin starts auto-attacking.

On private pirated servers, abusing this mechanic was very easy: one simply needed to make a macro including a /sit command: a character gets critically hit if struck while sitting. That is why many guides written between the death of official Vanilla WoW suggest this as a strategy.

However, there are a lot of claims that this combo does not work, and was only a feature of private servers, which indeed implemented many things wrong. On real Classic/Vanilla servers, one has to repeatedly press the X button and be in standing animation while struck — this is how it is described by most Paladin players correcting the “Reckoning stacking doesn’t work” statements.

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Now, my questions are:

1. Does either way of stacking Reckoning actually work in WoW Classic (1.13)?
2. If yes, how does one utilize it in PvP and PvE?
3. If yes, does one have to time the usage in a specific way? Does it require any training?