Newhalf implies futanari because futanari is the second most blacklisted tag on the site, and I think most people blacklisting futa expect it to include newhalf too. It's frustrating as a user when you blacklist a fetish you don't want to see, then posts keep slipping by because at some point futa fetishists decided that actually there are two categories, newhalf and futanari, and these are two totally different things, despite looking practically identical to everyone else.
Thousands of people blacklist futa and it's not reasonable to make them all change their blacklists or learn about all the different types of futa just to block a fetish they hate.
(For the record, the most blacklisted tag is yaoi. This would be like if yaoi fans decided that otoko no ko didn't count as yaoi, because they didn't like all that femme twink shit polluting their yaoi tag, so now everybody else gets to change their blacklists and learn how to block all these other forms of yaoi suddenly not included by the yaoi tag.)
As for post #4656301, it's telling to me that nobody has tried to tag it as hetero. Why not? If you truly believe this post is 1girl and 1boy, then it follows that it should be tagged as hetero. As far as I know, this person identifies as heterosexual. One could argue that by tagging it 1girl but not as hetero, you're still being transphobic, because you're not truly viewing the person as a woman.
One could further make the argument that the newhalf with male and newhalf with female tags themselves are transphobic and should be nuked. If you view newhalfs as women, then you shouldn't need these tags, you should just be able to tag them as newhalf+hetero if they're with a boy, or newhalf+yuri if they're with a girl. The existence of these tags implies that you don't view newhalfs as "real" women.
One could even make the argument that the newhalf tag itself is transphobic and should be nuked. The tag can be seen as an admission that newhalfs aren't "real" women, they're something else that needs separate tagging. By labeling them as newhalfs, you're not treating them the same as "real" women, you're objectifying them and fetishizing them based on their gender identity.
So be careful about calling people bigots for not sharing your point of view. The same arguments you use against others can be turned around against you.
We're talking about porn here, and porn is rarely politically correct. Just imagine the reaction if in that post she was fucking a woman instead of a man and people tried to tag it as yuri because it's 2girls having sex. I'm guessing that even the people arguing that she should be tagged as 1girl would be reluctant to tag her with yuri.
The point of tag what you see is that when you search for a tag, you get what you would expect. Would someone searching for 1girl or hetero expect to find this post? Probably not. Would someone blacklisting otoko no ko or yaoi expect this post to be hidden? Probably so. Would people get pissed off if you tagged a newhalf with female post as yuri? Yes, incredibly so. Tagging this post as 1girl isn't meant to be commentary on the real person it's based on, it's meant to categorize the post in the way that most users would expect.