Normally when laymen say "digitized" they mean one of two things: scanned images in a PDF or fully transcribed (and possible formatted) text extracted from the scan. The Complete New Yorker you're thinking of was mostly the former, with a bit of indexing (table of contents pointing to the PDFs if I remember correctly).

This latest digitization project does the latter, transcribing the text into their existing content management system and as far as I can tell, preserving much of the formatting. This comes with full text search, allows cross linking between articles, and all that good stuff.

I suspect that since they include an LLM summary and started this digitization project in early 2024, this was enabled by LLMs.