Lucy Gretsy is another like Sandy, she did hardcore scenes with men when she was younger but then resorted to doing lesbian sex in her formative years (with the likes of 'Red') and pegging only.
the guy in this movie was a known fucker of mature women in scenes, I think he did Wendy Taylor good and proper but yes, this has all the hallmarks of simulated sex with no penetration, it loses something without that but still good in it's own right. Now we may well never see Sandy do full blown sex with a guy, same with Georgie Nylons and Hazel May; the most we ever got out of Georgie were a couple of BJ scenes which were good though. There is no shame in it and enhances a performers profile by doing it in my opinion but at the end of the day, it's their choice.