Fermi questions[0] (oft maligned when asked in interviews) are a good practice for this sort of thinking.
Anything that is either out of range on scale, or that ducks the question, is worthy of further evaluation and at least some mild skepticism. Theranos promising hundreds of blood tests out of a thimble of blood would be the former. The article referring to Volts of electricity is like a car salesman replying to 'how many seats does it have?' with 'The seats are upholstered in Fine Corinthian Leather' the statement isn't incorrect, it is just useless and, in context, intentionally misleading. Salesmen do it to sell cars, scientists to sell research, journalists to sell papers, and conspiracy theorists for, whatever reasons, I guess.
[0] A few examples: How many piano tuners are in New York City? How many ping pong balls could fit in a school bus?