Chas, as already stated, when the fawn buck is born determines alot. That 2.5 you describe could have been a late born fawn with only a small spike rack his first year. I'm pretty certain biologists including Dr James Kroll conducted a expansive study years ago determining that spikes are not always inferior, but in many cases just need TIME(age).
If I remember correctly, the spike debate found that it was age/and or nutrition in most cases-not genetics. They proved their position by documenting several monster perfect typical 12 points that started as spikes in more than one part of the country.
Keep in mind, even in a fairly healthy "fair chase"(not high fence) scenario, with a herd expressing decent buck to doe ratios, there will still be some "late born" fawns. The "2nd rut" is usually healthy fawn does coming into heat and with that their fawns will be smaller and born later.
All this doesn't matter if there are "game stealers" on or near your hunting spot. They just caught a scumbag with 4 bucks at night next to where we have hunted and passed small bucks for several years. Pathetic.