I too see nothing wrong with photos showing a little more engorgement. As many have said it's entirely natural, and I agree it often enhances the look of a photo. Who's not done a little fluffing to make themselves look better? Really, I think the only rule should be against making the erection the focus, the point of the image... if it isn't blatantly sexualised, and we all have an idea of what that means, a cock in any state should be OK. TS exists for the sexualised side of things, after all.
I think it has way more to do with male shaming than anything else. Society prefers men who shave their faces -- so they look less like men and more like women*. It's ok that men have cocks and balls, as long as no one ever seems them. Although the tide is turning, used to be that Hollywood was more likely to show a cunt than show any cock at all.
In Missouri, a visible erection -- even through heavy fabric -- is considered indecent exposure.
Even within the nudist/naturist community, cocks tend to be shamed. Erections are a normal and natural part of the male body. No one was ever harmed by seeing a stiff cock. Yet, many (most?) resorts find them highly threatening and offensive.
* Please do not misunderstand. If you shave your face because that's what you want to do -- then all the power to you. Do whatever works best for you. I'm speaking of society in general that prefers men with shaved faces.
I enjoy the pics of a guy showing his erection. It is natural and nothing to be ashamed of.
Agree with so many of the posters here - erections are needlessly shamed. I enjoy showing and looking at erect penises.
A proud symbol of masculine virility, health and vigor.