"When did it become standard practice to issue suspension of benefits notices for plans that don't provide actuarial increases and that have suspension of benefits notice language? This might be more of a question for the old-timers.

I recall automatic actuarial increases for this becoming standard (worked at a large firm at the time) in the early 2000s -- perhaps 2004. I don't remember it from before that. Was the IRS pushing any plans, let's say, in the 1990s, to provide actuarial increases for failure to provide Suspension of Benefits Notices at normal retirement if the plan document stated the boilerplate (return to work) language only, and where the benefit was clearly defined as service and pay at late retirement date (presume over NRA, but under-70 1/2)?"