The original comment by SouthSamurai@sh.itjust.works:
Dammit, yet another question that I spent too much of my life on.
It comes down to nervesand tissue (cell, not paper) types.
The outside of your nose and the tissues of the anus are not the exact same. There's a different concentration of "nerve endings", and different types in different concentrations.
I doubt you want the full Monty of it, but if you look up the term "sensory receptors", you can do the deep dive very easily.
The short version is that we have specific types of "nerve endings" (that's what they're called colloquially, hence the quote marks, but I'll stop using those at this point). They detect pressure, temperature, pain/injury, etc.
The concentrations of them (as in how many per square inch), and the assortment of them (as in how many of each type in that square inch) varies across the entire body. The easiest way to demonstrate the relative principle is to touch your fingertip to your nose, your lips, your genitals (seriously), and your leg.
You'll find that your brain interprets the signals in an interesting way. It'll filter the less intense signals. You touch your finger to your lip, what your brain "says" is that your lips are being touched by something, and the signal from your finger takes the back seat. You touch the same fingertip to your thigh your brain says the finger is the primary sensation, and you feel the thigh via the finger rather than the finger via the thigh the way the lips worked.
Give it a try on whatever parts of your body you want. There's going to be a shifting perception of whether it's your finger touching something ( where emphasis is placed on the signals from the finger), or it'll be the section of the body being touched by the finger (signal from the touched location being emphasized).
The anus and the nose have different jobs. The anus, mostly, needs to detect pressure, injury, and some degree of chemical contact the nose needs less pressure sensitivity, but more motion sensitivity. So you'll get a different overall sensation with any given substance that's pushed against either, and when the same substance is moved across either. The difference may end up being minor. But both are sensitive enough that most people can tell a difference between paper tissue products blindfolded.
Back in the day, I wiped asses for pay. The only patients I had that couldn't tell the difference between brands of TP had medical issues that interfered with nerve signals. Do a test for yourself. Find a buddy to hand you tp or facial tissues and keep a log (heh, he said log while talking about butts). There's a very good chance that every single one will feel different. You'll probably be able to tell which brand is which if you've used that brand before.
You can probably even tell the difference with your fingers tbh. But you wouldn't likely be able to if the same products were placed or rubbed on your back
You'd also notice that different objects will feel different when just placed on an area and pressed gently into the skin vs when you wipe the area with it.
Skin is an amazing thing. It's armor, a sensor array, a biological filter, sunscreen, and a temperature regulator all in one! Plus other functions tbh, but shit like that gets overwhelming to read for a lot of people
You'd be amazed what you can discover with just an hour sitting around and touching things to parts of your body.
Checked the temperature of the ceiling?