The are so many factors that go into antler development, and genetics is only one part. There is environmental factors, feed, nutrition, minerals, etc.
The idea of "once a spike, always a spike" is complete fiction. Used by folks to justify shooting a deer.
While I'm sure there are some deer that remain spikes after the first year, the number/percentage is really, really low. More common - and more correct - to say they may always inferior deer - but even that is not always true.
For example, a late buck fawn may only grow spike within his first year, due to short season/development- but may blow up to a nice 8pt the very next year, and continue to add points and mass after that.
Even inferior genetic deer, with poor nutrition, that are initially spikes are more likely to be a fork the following year, rather than continue to be spike.
True spikes - a 3 or 4 year old - are, IME, actually pretty rare.
I have witnessed with my eyes a spike (with a torn up ear - easy to recognize) turn into a wimpy basket 8 inside the ears in his 3.5 year.