I get that these are things you might do regularly and feel more empowered to use Siri for them... but they're rather banal and could be done with literally a one or two step process previously, especially if you're already using Apple's first-party apps which seem to be a requirement here. In both email cases, Spotlight handles searches like that just fine, and moving a calendar event only requires clicking and dragging.

I'm here wondering why so much extra space is warranted, or how to take it back, not so much how I can find a document with specific text in it or use Siri to do something else that was already very easy.

One task I'm wondering about is for example, asking Siri (on the mac) to analyze a huge dump of arbitrary PDFs that may or may not have non-OCRed text in them, and efficiently reorg and rename them based on what the documents should be. This also seems like a mundane task, but requires a little more than just a standard search and would allow someone to take their entire paper archive of private business documents and create a digital archive without too much risk or work. This is something that all local models I've tried so far really struggle with.