Probably grafted. If so you should be able to locate the graft union. Either near the base or perhaps higher up if the tree is a standard. Whether it will grow true from 3 feet depends on where the graft is. But why do you need to do this? It would ruin the habit of the tree. Has the top died?

How about some photos?

The top died but kept the base just in case there was new growth; to my surprise there was.

https://www.monrovia.com/plant-catalog/plants/4599/royal-raindrops-flowering-crabapple/

link seems to indicate leaves emerge red... and deepen in color ... if would seem you are on the right track ...

speculating ...... i would NOT expect mass produced understock to have red leaves all season ... i would then confirm.. if the flowers eventually .. in tree time... still fit within the description ...

i have red versions of crab ...that have all the root sprouts.. that are green .. so i would suspect.. the root mass is what was grafted ... they not being a red version ...

ken

I did buy another to replace since I don’t want to look at a stump for the next several years; I have a rehabilitation area for the injured I use to experiment with. If it bounces back, great....life is too short if I may echo Ken :)