Actually, I misrepresented what Giddins was saying. Rectifying that with a direct quote from his liners for 12!:
"...perhaps he has been too visible. As one of the most frequently recorded jazz soloists, he has inevitably put down some uninspired music and a lot of people, this writer included, passed over what he was doing. Last year we had cause to wake up. For one thing, Sonny was travelling with the Giants of Jazz and playing well, sometimes brilliantly. For another thing, a record called Tune-Up! was made, with three exemplary compatriots (Sam Jones, Barry Harris & Alan Dawson), and it caught Stitt playing with astonishing imagination and verve..."
He's tracking pretty much with exactly what you're saying. And btw; these liners were written in/around 1973, so that Giants of Jazz tour would have been 1972. Tune-Up! was recorded in February of '72.