Get tag quality in an expression

[WillMT10]

From that same thread I linked above:

@pturmel

When you use the tag() expression, it has to go get that value for any re-evaluation of that expression, including an actual tag value change. When you break it out to an indirect binding, that binding will only make a request when the path changes, and sits waiting just for tag changes otherwise. The expression will re-evaluate on the new tag property change, but other reevaluations will only grab the subscribed tag value. Much more efficient.

If you were to use tag() functions extensively, it can get A LOT more sluggish than using indirect tag bindings (learned this the hard way...).