Apple’s copy / paste mechanism contains multitudes.
When you copy something - many levels of data are stored into the pasteboard object - literally a reference to these apps is available to any application that receives a paste command.
You can start on understanding this rich and complicated behavior with two items:
- An excellent app to show you what’s really on the pasteboard
- An excellent write up on how this all works.
For #1 I recommend the pasteboard viewer - https://sindresorhus.com/pasteboard-viewer - it’s on the MacApp Store and also source code is available under the MIT license.
For #2 I recommend the writings of Howard Oakley - his dives to the depths of the code and implementation yet writes clearly and in accessible terms. https://eclecticlight.co/2020/05/12/cut-copy-paste-inside-the-pasteboard-clipboard/
When you paste an item from the clipboard, its data are passed to the requesting app, which then performs any conversion necessary, and inserts it in the document.
So to answer your question, it’s possible you have all of the various resolution of the icon images pasted into your document, but I would need to examine either your document or your exact pasteboard contents prior to pasting to answer your question. Hopefully the general answer above helps everyone as well as you dig into specifics.
RTFD documents are plain text with attachments, so you can examine them in the command line or control click to show package contents just like other folders in Finder.