It all comes down to what exactly you're using when you cut the sub-light engines. Do you use different engines for lightspeed or are you just cranking down, like shifting gear.
And it's very important what kind of parsec we're talking about. Yes, Han's from Correllia, but many others are obviously aware of the concept "kessel round". So which parsec's more familiar in the Empire in the time of ANH: the Correlian of the Malastarian parsec?