My DD exhibited a similar rocket like launch into reading. She had been faking it, We sat down together and I made her sound out the words one painful Saturday morning and something must have clicked. She just took off!
She would also take forever to write stuff down, whole races of bacteria flourished and then went extinct just during the time she spent writing a a paragraph, I am sure.
I think in her case it was perfectionism and being afraid of looking too geeky so she would dumb things down to fit in which wasn't natural for her. She is a lot more comfortable now with this stuff (5 years later LOL).
Open ended assignments would paralyze her with trying to process the myriad of thoughts that flooded her head and pick only one...
