Did you trace the stem back toward the plant to see if it is attached to the same plant or maybe something else that sprouted up?

I double-checked it this morning, and yes it's from the very same plant. I can take a better photo if needed. Maybe it's a hybrid and the severe pruning somehow triggered the foliage of one of its ancestors.

There is a condition called fasciation that causes abnormal growth, usually thickened stems. You might want to check that out. The causes can be varied, but I've seen more of it this year after our heavy rains, and it can be weather related.

That is not fasciation. If anything, it looks like a reversion that may have been caused by severe pruning.

btw, fasciation is not weather related. It is primarily caused by a hormonal imbalance or by a genetic abnormality but can sometimes be associated with a phytoplasma or bacterial infection. It can appear very randomly but in many cases is a stable condition, like with crested cacti, various conifers and with celosia.