What's up with pooping in diapers?

So my 2 and 3/4 year old is pretty much potty trained - this is my 4th kid so I really didn't give shit whether or not he did this heroic deed early or not. My other 3 kids all PT-ed by 2 years which I took personal credit for until this one showed up and ruined my average. Anyway, he has an accident here and there but generally is doing really well. Except for pooping. He is all hung up about needing to be standing to poop which means no potty. I actually tried to convince him to stand on the toilet and just aim but he said "hell no" in Baby Coleman speak. Which is a loud, guttural yell. I ran out of diapers and I cannot bring myself to spend $15 on shit catchers, you know? I have been buying the organic, dioxin free type because his skin is really rashy but it seems really just plain old dumb to do that for a quick poop and toss kinda of situation. Then I got a mental block about buying anymore at all. It just seemed wasteful on so many levels. Plus, I thought that eventually he would get so backed up and so uncomfortable that he wold figure it out. Which I am sure he would have if it wasn't for his kind father who couldn't stand to see him suffer.
What happens is he feels the need to poop but maybe not, maybe just to fart because he hasn't pooped in 2 days - he isn't so sure - all he knows is that his stomach hurts. So, he panics and he yells, "pooooop". I put him on the toilet, he sits there (now he actually, I kid you not, from my midwifery coaching of him, says, "breath - good, in and out, just relax, you're doing great" or he sings the "everybody poops, sometimes" songs sung to the tune of REM's "everybody hurts.....sometimes, and everybody cries.....so hold on..." - you know that song that makes you want to slit your wrists? So, he is self-soothing and then, poof, "it's all gone momma" and nothing has happened. The gas has passed I guess. And he is off and running.
So, I had the brilliant idea of putting some underpants on him the other night and telling him they were like diapers, to go ahead and poop in them. You have to know that none of my kids wear underwear (well, Ellie, my 14 year old does now of course) - don't ask me why - they all reject them 100%. This worked like magic - I tossed the poop and washed the underpants and we were golden.
I am just starting to feel like this whole ritual is sort of enabling his inability to just bare down and get to it on the actual pot itself, you know? And what would a real babysitter say about having to deal with this method. I mean, Ellie is repulsed enough as his babysitting sister. For God's sake - we have to have some standards around here, right?
My sister in law had the same problem with my nephew but they worked through it together - right there on the toilet - the spot where most important and intimate things occur in all families but no one will admit it but me right here and now.
Now that I think about it - I have had the most profound moment of my marriage, right on the toilet, in labor. I actually became my husband, and I think (I'll have to ask him) he became me.
Ok, off to bed for the night.