Although I'm confident about my theory/suspects I've already said in posts I can't be sure of the motive. It could range from altruistic, raise as own, to sinister, Brady/Hindley.
If raise as own we've already covered that there's no evidence the blemish/mark in MM's eye was an actual Colombo as per her passport etc. When PJ asked the McCanns about identifying features they refer to a blemish/mark in her eye and some sort of birthmark on a leg. From memory I don't believe KM's book refers to a Colombo.
Re childhood memories all the research shows
Most people have no memory prior to three years of age, and few memories between three and six years of age, as verified by analysis of the forgetting curve in adults recalling childhood memories.https://en.wikipedia.org/wiki/Childhood_memoryIf MM was abducted to raise as own and her abductors a) stuck to a story early on 'why her parents parted with her' or how she was 'found' and b) thereafter provided a good home her loyalties will switch to her abductors which she might well have been with for 75% of her life now.
An anology might be religion whereby a child brought up in a home where religion plays a significant part of daily life will in all probability follow suit. Conversely a child brought up in a secular home will in all probability follow suit. The same can often be said for political allegiances too and even football teams! Beliefs are formed at a young age and shaped by what goes on in the child's environment. Of course once the child reaches adolescence/adulthood then he/she might challenge their own beliefs but imo this is not the norm.
You can see with KM she has herself down as a Catholic and Everton supporter as this was how she was raised. In her book she says she did not at any time question her Catholic faith as this was simply how she was raised.