How so?
Innosilicon has been quite consistent in their naming scheme - except they never got around to actually releasing the A3 at all (I've seen commentary that the A3 wasn't going to be efficient enough to compete by the time it would have been released as WHY Innosilicon never pushed it into production).
It's a bit confusing / misleading because the A4 mines Scrypt, an entirely different algorithm than Dash which uses X11, yet the devices are named sequentially as if the new machine is an improved version of the previous one which is not the case since it's an entirely different algo. This is not out of character with their product naming though, since the A1 mined bitcoin.
Typically naming schemes for machines follow unique identifiers for the type of calculations the machines do. Antminer S9 = SHA256, Antminer L3+ = Litecoin / Scrypt, Antminer D3 = Dash/X11 - easily identifiable as to what type of coin they're designed to mine by the letter used for the series of device.