Please don’t forget about 2nd definitions of words, and idioms. The stylistic note here is to be really careful when language policing. From what I’ve seen, it’s almost always wrong and backfires looking bad on you to claim other people’s word choices are incorrect. I know this from plenty of experience being knocked off the high horse. ;) But language is broader and more fluid than we imagine, and it’s quite fun to be a student of the way language works and changes over time. In English it gets even more fun when tracing etymologies through the other languages where our words came from and see the weird subtle ways the meanings change.

knell (noun) 2: “an indication of the end or the failure of something” https://www.merriam-webster.com/dictionary/knell

spell (verb) 2: “to add up to / MEAN”, 3: “come to understand” https://www.merriam-webster.com/dictionary/spell

Examples of the idiom ‘spell a death knell’:

https://www.npr.org/2020/05/28/862658646/the-latest-u-s-blow...

https://www.couriermail.com.au/news/queensland/gladstone/spe...

https://www.mca-marines.org/wp-content/uploads/Machine-Learn...

https://www.protectingtaxpayers.org/international/to-shield-...