MySQL EXPLAIN doesn't show 'use index' for FULLTEXT
I can understand why this happening
You only have one row in the table.
MySQL Query Optimizer will execute a plan around this rule-of-thumb : If the number of rows needed to examine the fulfillment of a query through an index exceeds 5% of the total of number of rows, the Query Optimizer will not use the index and will go with a table scan or an index scan instead.
How many rows in the table ? One
How many rows are indexed ? One
Since you will be examining 100% of the rows, a keyed lookup will not chosen. The query will be executed. You simply do not have enough rows to justify getting an index involved in the search. This applies in general for anything indexed. FULLTEXT indexes tends to get thrown the Query Optimizer under the bus at the most inconvenient times. I wrote about that back in Jan 26, 2012.
Try loading more rows into the table, at least 21 rows, and try again.