I'm very well read, but fairly new to gardening cacti. With that said, i will share a recent occurrence.
We cut 2 similar cactus down to a 8 inch or so well rooted stumps. The pots were both taken indoors to heal for about a month+.
Once back outside, 1 was buried over loosely. The second was left to stand at the same depth as it had been pre-cut.
The one we buried had 3 new tips starting after a couple weeks. The other had none after 3.... so we buried (loosely) it as well. A week later, it has 1 new tip starting.
Buried loosely= brought soil mix level up to cover all but the top 1/2 inch and then tossed a couple handfuls over the top of the stump. It was covered but by the time I noticed new tips, about 30% was uncovered.
I'm not sure, but my guess is that IF covering did anything, it forced the cactus to grow a new tip for need of sunlight.
It may have just been time. . . . I have read that you should leave a foot above ground to give the cactus enough sun power to grow the new tips vigorously.
I'm just learning too, thought I'd share.
All posts written by Madcap should be regarded as fiction.