I suspect this may be a wish from BBC for marketing reasons. With the way the show has been hemorrhaging ratings in recent years, they need to go balls to the walls to get high profile interest in the show again. Bringing back Tennant, one of the most popular Doctors, even if just temporarily, is probably viewed as a worthy enough gamble to do that. Plus Donna, a fan favorite companion played by Catherine Tate, who was already a well known celebrity in Britain even before she was involved with Doctor Who. It'll get noticed, at the very least.
I wonder how these same people felt about Noel Clark doing a photoshoot in his underwear for DWM, or a DWM interview with John Barrowman where he talked on and on about his penis. It's funny to think shirtless Gatwa is suddenly "too gay" compared to what's been in this magazine in the past.