That's simpler indeed
The big difference is that you do your tag editing in Calibre itself (i.e., in the Calibre database), and I do it outside, directly in the book itself. This means that I have to do the import twice: first to de-DRM the book (and then copy/remove it), and import again to get it into Calibre with the correct tags.
I could drop the Sigil part, but I don't like any whitespace in between each paragraph if I can avoid it. It costs me just a minute to add those two margin properties, at least in a WELL MADE BOOK, that is.
The newer ebooks I've been buying yesterday and the day before are much better than the older ones I bought some time back. Sometimes, a paper version gets a re-issue with a different cover, sometimes a different font, and that's about it; would they only change the cover on the ebook, or also update the layout and coding, if it was bad in the old version, I wonder? I'm not going to buy the same books in 2 or 3 years to check...