I've been growing avocado seeds. I have several now anywhere from a year old to about 4 yrs old. So I've been experimenting.
I wish I had a side-by-side photo to show you.
REMEMBER THAT THIS IS FOR GROWING AS AN INTERESTING HOBBY HOUSEPLANT. The pruning criteria and technique is likely to be different for in-ground grown, grafted, fruit-bearing avocados.
If your plant is experiencing explosive growth, this is as good a time as any to pinch the top. If you have a long thumb nail, select the first leaf petiole from the top ABOVE WHICH you can successfully cut with your nail LEAVING about 1/16" or 2mm of UNDAMAGED stem above it. Pinching crushes the stem so take that into account. (You can also just pinch at random and clean up the cut later after further growth will reveal the best spot, but doing this, you can miss the ideal bud to grow out)
All in all, the growing tip pinch is the only time thumb nail can do the job. Otherwise, I often use toenail scissors for indoor plant pruning, and regular pruners for anything thicker than 1/8"
Another selection criteria is just above a cluster of leaves or visible bumps/protobuds so more than one bud will be stimulated to grow into a side branch.
I have also tried viciously hacking off just above the first full-sized leaf. This works well in stimulating a new sturdy LEADER but usually it just takes over the plant and usually at an angle.
And I've tried cutting above the tiny leaf below the first full-sized leaf. The result was same as above when done during good growth like early summer, but when done during the cold winter, the whole thing died.
I have another one that, at about 3" I actually chopped off just above those teeny, tiny not-quite-leaves that are clustered about 1 inch above the seed. This one resulted in a pretty much perfectly even double trunk (or 'Y'). I did it in winter time and it sat and didn't do anything for 2 months -- I honestly thought I killed it -- but then it started to grow about this time of the year.
So, you see, THIS is why you're seeing conflicting information. Pretty much anything goes as far as getting the avocado to grow a new shoot after cutting. The trick is getting, what is to you, a pleasing shape out of it.
Go for it. Have fun and good luck.