The "virtue signaling" is signaling being a scrappy creative type who regrets/disliked the path he followed when he actually sold out to a big conglomerate at the first possible opportunity. The virtues being signaled are things like independence and grit.

Perhaps you read a different blog post than I did, but that's not what he signalled at all. He regrets getting involved with ESPN specifically because it was a poor fit for him as a television network that didn't have a suitable business model for 538, and would have preferred if he had taken the competing offers from NYT or Bloomberg in 2013 and then wanted to move to The Athletic in 2018. At no point did he say anything like "I wish I didn't sell 538 and stuck it out alone".