The consensus of expressed opinion so far is that if you are, we all are.
The precondition hasn’t been documented, it just appeared one day. ST are funny like that. They do something potential unpopular and broadcast it from the rooftops, but long requested features just creep in unheralded. So we never get a convenient place to say nice things, ask questions, and report bugs. Yet when it comes to giving them a good shoeing, they make it easy for us.
But I digress. I think we all assume that the precondition is supposed to be like the ‘only when’ / ‘restrictions’ / ‘limitations’ / whatever we see on many rules based systems. That is to say something that has to be true for the automation to proceed, but not something that itself triggers it.
Essentially it has been assumed to be the missing link that is intended to let you do ‘if A or B or C arrive home, but only if the mode was Away at the time’ without worrying about a race condition when Away is set. This is key to being able to accurately replicate the behaviour of Routines.
You have also illustrated another case where it should enhance functionality. It essentially permits the “(if location mode is Home AND (A or B or C happens)” conditions that are missing. In this example it possibly wouldn’t matter if it triggered when the mode changed, but that is moot as you can’t do it.
It has been observed in more than one thread now (and someone more diligent than me may come along and link to them) that the precondition just doesn’t do anything when used with the ANY condition group. If it isn’t a bug no one can work out why not because it really ought to be. The one specific use case where it is absolutely critical, turns out to be the one where it doesn’t work and makes things worse.
It also displays in a confusing fashion when there is only one other condition, but that’s an extra issue.
Extra: Without even realising I’d done it, I found myself on one of the threads. This is the first report I saw of it. It took a while to realise what was happening because I don’t think any of us thought it was credible it didn’t work.
It is something that is worth reporting to support if you have support that responds quickly as it raises awareness. It is the sort of thing we have to suck up in the UK as our current response time is in excess of a month. So it is a bit ‘Dear Fire Brigade, FIRE, FIRE …’.