I'm not sure this is correct. According to one source[1],
"The name of a newly discovered exoplanet is dependant on the name of the star which it orbits and also if any other exoplanets orbiting the same host star have been discovered. The first exoplanet discovered around a star is given its host star name with ‘b’ appended. The next exoplanet discovered in the same system gets the letter ‘c’ appended and so on. Planets in multiple planet systems are always labelled b, c, d… in the order of discovery."
It's not clear to me why they would begin with 'b' instead of 'a', but basing the order of names on the order of discovery makes intuitive sense. The largest planets would presumably be discovered first, even though they may be in the middle zone of their systems (such as in the Solar System).
EDIT: Kepler-26[2] is an example of the named order not matching the distance from the star. The planets in that system, in order of distance from their star, are: d, b, c, e
Yep, you understand it correctly.