A setup is a defined pattern or condition with entry, stop and exit rules, for example a pullback to a moving average in a trend or a range breakout. Tagging records which one you believed you were trading each time.
The comparison is the reason to do it. Average result in R by setup shows which of your methods carries an edge and which only feels active. Many traders discover that one or two setups produce nearly all of their profit while others quietly lose.
It also exposes trades that fit no setup. A growing group of untagged or other trades usually means improvisation, and that group often has the lowest expectancy of all.
Tags work only if they are assigned at entry, before the outcome is known. Tagging afterwards lets hindsight choose the label. If you have to invent a new tag to justify a trade, that is information.
As with all comparisons, watch the sample size. A setup with eight trades has told you very little, whatever its average says.
Reflect does not tag setups itself; it analyses time, session, sizing, plan adherence and re-entry timing, so keep your setup labels in whatever notes you keep with each trade.