Not new at all
"Attacks that swamped telecoms services are a much more recent innovation, first starting around 2010"
That is absolute rubbish. I am very aware of an incident over 20 years ago where a business that relied on incoming calls was hit very hard by miscreants constantly calling their number meaning customers couldn't get through.
Because of the type of business they were in, customers very quickly moved to a new company and they didn't build back up the customer base they lost in those few days.
It's a very nasty way of hitting the competition. Should be easier to block / trace these days though.