Unfortunately there is no readily available information on the "meaning" of this nursery rhyme other than a tiny wiki article that just says it's a simple counting lesson with some base information about where it was first published. I'm also pretty sure it means exactly what it means and it's purely a simple counting lesson with no darker or complex meaning.
I started looking into what it means because I found out there is this darker interpretation of the very first line that the piggy was sent to market/slaughter. It was interpreted by some random person on Twitter the first time that way around 6-7 years ago. This same thing is still being passed around. I just recently saw it flash through my Facebook feed for the first time recently and I had never heard that or thought that. I don't trust things I read on Facebook, so immediately I start researching this.
I've researched a bit about nursery rhymes and yes a lot do tend to be morbid, like Ring Around the Rosey. But I feel like if it were a dark or complicated nursery rhyme, there would be some information somewhere. At the very least something about it in the wiki. I feel there would also be some older information about this darker side somewhere seeing as how that only gained traction through Twitter, so much so that some old dude wrote an opinion piece in the Chicago Tribune about what he heard the Twitter user say declaring that holy shit the Twitter user must be correct and why did I never interpret this counting lesson as a dark message that that piggy is going to be slaughtered.
I feel the Twitter author just went to the dark side with their interpretation assuming that all nursery rhymes have a darker side, which isn't true. They aren't all morbid, just mostly morbid. Above all else nursery rhymes were meant to teach kids important lessons.
I also feel that if there were a complicated side to this nursery rhyme it wouldn't have been "discovered" by a random Twitter user and knowing that Twitter is about as informed and knowledgeable as Facebook makes the author of the Chicago Tribune piece less than reliable.
And honestly overall if you want to think it means your piggy (slang for toes) is going to be slaughtered, good on you.