It doesn't really matter if the plant is tissue cultured or not. That isn't the important part of your situation. The important part is, that is the incorrect way to overwinter that particular type of alocasia.

Brancifolia, Stingray, advincula, Nishihira, reticulata and zebrina (and others LIKE them) do not respond well to the treatment you have described. These are very, VERY finicky plants, probably among the most finicky of the alocasias. They will rot if kept too wet, and they will go dormant if they do not receive the light and temperatures they want.

The best way to winter them is to just leave them in the container, bring them into the house, and put them in a sunny place and don't overwater them, and if they look like they are deciding to go dormant (leaves start to die off, any new growth gets smaller, etc) just stop watering almost completely and let them sit til it warms back up and daylength gets longer.

The main stalk may or may not die off, but it generally does, and it should produce several really small satellite tubers (they are usually only the size of a thumbnail) that will regrow new plants when conditions are optimal. But don't ever remove it from the soil completely and disturb the root system, or you will probably end up with nothing.