doc.rasterize() at 300dpi not possible on a Large Canvas yields 30dpi

How large is the document? If the canvas size is beyond normal 227” limits I can’t help to ask why anything would need to be rasterized at 300ppi. The rasterized elements would probably cause the file size to be enormous. Most large format printing work is done with pixel-based elements set at far lower, more manageable dpi levels.

Yes, there are known problems with resampling in Large Canvas Size documents.

When saving as PDF, when Cropping and as you noticed when Rasterizing.

https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs/suggestions/47439314-pdf-files-made-on-large-artboards-get-downscaled-i