> Yes, and where would they have noticed that penalty?
In a drop in incoming traffic, so with whatever they're using for analytics.
In all honesty it's probably just a new SEO consultant trying to clean up past sins and move on with whatever the latest grey hat strategy is.
IMO it's a gross overreaction to a form letter that a high percentage of webmasters have received.
> It's quite likely they noticed a penalty...
Yes, and where would they have noticed that penalty?