The terminology 'hard' vacuum is not quantitative, and rather vague; there are arguments that state a hard vacuum is 1 Torr while others state it at .01 Torr.
If you wanted to qualify a 'hard' vacuum you would be in the realm nearing that requiring a McLeod Gauge or Ionization Gauge.
It is easier, here, to refer to vacuum in terms of either Microns or Inches of Mercury; these terms are more commonly found on the gauges, equipment and charts used in Air Conditioning.
Is it 'practical' to attempt to evaporate or remove all of the moisture in a
water soaked drier? No, because it is possible to pull a vacuum down deep enough, quick enough, that water liquid turns into a solid (ice) before it 'evaporates' or is removed by the vacuum procedure.
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And, another issue not often discussed in terms of an evacuation procedure, is for instance when converting from R12 to R134a: for those whom attempt to save a few dollars by not replacing the drier with a new one. Refrigerants become trapped within the refrigerant oil within the drier. Hence, if you think you recovered or evacuated out all of the R12 prior to inserting in R134a, you will be surprised to find that you have not. Refrigerants can remain entrapped within the oil in the drier.
It is SOP (a Standard Operating Practice), to replace a drier when it is old, when changing refrigerant and oil types and after a compressor lock up or seizure.