No. They did not become a fractional reserve, they became insolvent. A large portion of the BTC community grossly abuse the term 'fractional reserve', and it's flatly wrong.
Fractional reserves refer to liqudity, not solvency. If I run a financial institution and I owe depositors $100, but have $10 cash and am owed $100 on top of that, I'm running a fractional reserve.
If on the other hand, I'm MtGox, and I owe depositors $100, but have $10 of cash and am owed nothing on top of that, I'm insolvent. Bankrupt. And if I keep operating, I am a fraud.
Fractional reserves refer to liqudity, not solvency. If I run a financial institution and I owe depositors $100, but have $10 cash and am owed $100 on top of that, I'm running a fractional reserve.
If on the other hand, I'm MtGox, and I owe depositors $100, but have $10 of cash and am owed nothing on top of that, I'm insolvent. Bankrupt. And if I keep operating, I am a fraud.
This is an incredibly important distinction.