A different purpose
A cup at home is made to be enjoyed, so the brew is adjusted to flatter the tea. A taster's cup is made to compare, so the brew is held constant, and is often stronger than anyone would choose, because strength makes differences and faults easier to find. A tea that cups well is not necessarily the one you would want to drink, and the reverse is also true.
Why preparation is standardised
Comparison only works if the samples were treated alike. ISO 3103 is the international standard for preparing tea liquor for sensory testing. Its purpose is to make such tests repeatable, so that a difference between two cups reflects the teas and not the preparation. It is a method of preparation, and it does not say which tea is good. TeaHQ refers to it and is not certified to it, and the standard itself is published by ISO.
Repeatability and calibration
A professional's judgement is worth something only if it holds from day to day and agrees with colleagues. That is why panels taste together, compare against reference samples, and taste blind. Trained tasters still disagree, and the disagreement is informative rather than embarrassing.
Looking for faults
Much of a working taster's day is spent on rejection: spotting smoke, staleness, taint or poor firing before a lot is bought. A fault found at a sample table costs a sample, and a fault found after purchase costs a shipment.
What to borrow, and what to leave
Borrow the discipline: fixed weights, fixed time, one variable, notes on each sense. Leave the strength unless you are looking for faults. The point of learning this is to notice more when you drink tea for pleasure, and tasting should not turn every cup into an exam.