Before you wish for a rail, consider what lights might fit on such a rail. The 43x is supposed to be a cross-over between the 43 and 48. The short slide is flush with the end of the dust cover. If you make it flush with the end of the 48 slide, like a 19, it is no longer compatible with the short slide. That defeats the purpose. So we keep the short dust cover and add a rail. It isn't long enough. The G43 barrel length is 8.6cm, the S&W M&P Shield 380 EZ barrel length is 9.3cm. Or in Imperial terms, a shade over 1/4" shorter than the Shield EZ. And since the Shield EZ's dust cover doesn't go all the way to the muzzle, it's safe to say they are about the same.
I bought a Shield EZ for the purpose of giving it to a friend who has strength issues due to nerve damage. And to set it up properly, I planned to slap on an Olight mini-Valkyrie light. After all, the Shield has a rail with 3 slots, so a light must fit, right? News flash, it doesn't. The smallest detachable light is too long to latch on. A TLR-1 won't fit either. The only one I can find that will is maybe the Inforce APL. The Recover Tactical rail doesn't look long enough to handle anything useful either. So the bottom line is that Glock can abandon the "x" concept to give the 48 a long enough dust cover to have a working rail, or keep the x. They chose the latter, and at least for now, I think that was the better choice.