We know the processor is ARM, but I'm not sure any of us know specifics about the environment beyond that (and the fact that it's mostly Java plus Groovy). But my guess is that it's also a very small computational price to pay. When we hear things "simpler" in an app context here, I'm never sure if they mean "simpler for users" or "computationally less complex," so I didn't mean to imply anything there either way. But it is what it is. 
One solution I've seen is to wrap the entire rule in an IF THEN whose contents will only execute under whatever conditions (mode, etc.) you want, but a simple idea I alluded to above is pretty easy and with a simple conditional only takes a few clicks (and for any combination of modes can still be a "simple condition" even if you combine multiple modes or negate the expression, as below):
I'm sure you know this, so just posting for anyone who is wondering. I don't think the previous feature is likely to return. I also found the post I was thinking about when I wrote the above in case you are curious more about the history and reasoning behind this: