CorBlimey is correct (sometimes these ex-Brits can be pretty smart - infact the "Ex-er" we get the smarter we seem to get. Just kidding - I can get a away with that, 'cos I'm one too

..... are you strictly speaking "ex" yet CBL? - I recall you were talking about spelling differences the other day. I've been US so long I only goof on the "s" and "z" thing now and again and when I open my mouth the Brits think I was born US and the Americans still hear the Brit accent!!!. Guess I speak "mid-atlantic"!!
Back to business.... Assembly cuts a - ie: NOT in-context edits of the PARTS, but cuts done on the actual assembly - are intended to mimic real life. In other words, if what you actually do when you manufacture, assemble the parts FIRST and THEN start cutting on the assembly.
Ref your comment on castings, the way we do castings is this:
One part for the casting/machined casting. Two configurations - cast and machined. There is endless debate on whether you should model first as machined (finished part) and then add the machining allowance in the cast configuration - or - Model as cast and remove it in the machined config. I was adamant about it at one time, but I've mellowed with experience. Acutally I don't think there is a hard and fast rule that seems to work best in all circumstances - it depends on the feature you are dealing with. So I'm not about to beat anyone up for their choice on that.
Now if you are like us and include "non-separable" items in the machined part drawing (like press fit pins, bearing, etc.) what we do there is use a SW assembly as the machined "part". We do this because we do not machine product here - it is all sent out.
So I don't see any need for (true) SW assembly cuts in castings per-se.
You could also use a casting part as a Base Part for the machined part file. But we found no advantage for that for our purposes. It does also force you to pretty much model as-cast first. Which, since most design is done as finished, would probably result in you doing a fair bit of to and fro in an assembly or at least the machined part file working on the casting part!!!! ( But I still don't see any assembly cuts..)
I was - and he did. So at least I didn't get coal.....
OK, OK, It's a reference to my holiday sig. "Be naughty - Save Santa a trip..."