Its pretty obvious. The NSPCC haven't said this is fine. They fully support people's (men's) fetishes. Exhibitionism is a fetish. So are they now discriminating between fetishes?
The NSPCC is happy for men who identify as women to flash their penises at 5 year old girls in changing rooms. They fully support that. So what is wrong about doing it in a supermarket aisle? The child wasn't expecting to see it? Does cock look different when it's in women's changing rooms?
So no, the NSPCC haven't come out and supported this, but it's actions would suggest that it'd be on shaky ground if it tried to argue this was wrong but it's other policies are right.