I'm not sure Edison is known for his imagination. He was well-known for his workaholism and for performing hundreds or thousands of experiments until he finally found a combination that worked (in his lightbulb). I think in his case LSE is not hard to believe.
I'm not sure how many socionists are serious about Da Vinci being an LSE. I don't have an opinion.
"LSE lacks imagination" is too broad a statement to be correct. There are different kinds of 'imagination,' and imagination or abstract thinking in general is also tied to IQ. The fact that Edison was an experimentor and preferred hands-on applications as opposed to paper-and-pen theorizing is a good argument for LSE over, say, ILE, ILI, or one of the other "imaginative" types.