Tangs aren't my specialty so hopefully someone else will answer (Dude, I know y'all are lurking out there - You know who you are!)
I wouldn't use the terms "recessive" or "co-dom" with tangs and CT's since they're line-bred...but I have heard that there may be a genetic basis for such colorations based on some wild-caught leos.
Some HTs and some SHTs are like BAM! straight out of the egg. They come into the world with that coloration and that look where you can be like "YEEEAH! that one's gonna be killer!". A few are surprises. The educated eye can identify the super-hypos and soon-to-be CTs from birth, but there are always great surprises with leos as they shed and grow. I love that!
At first glance, hatchlings that will turn out to be nice hypos, perhaps with a passable degree of carrot-tail, can look VERY normal. Dark bands and all. The absence of those black "handles" on the rear legs plus increased tang coloration in those areas and an increasingly faded appearance to the darker bands and areas typically suggests that the baby will hypo-out to a major or minor degree and develop a deeper tang coloration than the average normal.
Wow...sorry for rambling! Perhaps someone with decent pics will respond with their hatchlings (I couldn't take a decent photo if someone put a gun to my head).
Here's a crappy pic of what turned out to be a HT with a fat chunk of orange base of beginning at the base of her tail. Note the "fading" around her dark bands, lack of dark "handles" on her hind legs, and increased tang on hind legs. Definitely not quite enough consistency to be called a carrot-tail and she's nothing special, but heck, she's now a beautiful, fat, deep hypo tang with great tail coloration and she looks like a different leo than her baby pics.

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Too many Leos
1.0 feline "Spot"
0.1 canine "Tika"