Against Ryuma, it wasn't. Zoro went right at him, cut him up in close range, and then came out the other side.
But against Kaido, he didn't move forward with his attack, he was still in the same spot in the air after he released the attack, it was a flying slash this time around. If it wasn't, Zoro would be on the other side of that horn, but this time he stayed in front of Kaido after releasing the attack, instead of going past him like Ryuma.
Here you can see that Zoro throws the slash, and then right after Kaido is shown in front of Zoro again, just like when Zoro used the attack.
And here...
We can see that Zoro needs to get up and close, and then past the enemy.
So yeah, it seems the attack has evolved from a close range to a long range attack using haki / ryou and air slashes.
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You could also say that Hiryuu Kaen was always a long range attack, there's an argument for it.
Think about like this, Zoro was trying to send out a flying slash against Ryuma in Thriller Bark, just like against Kaido. But because Ryuma had Brook's shadow, he tried to use Brook's techniques that are always close range and get past the enemy, so Zoro send out the flying slash, but Ryuma was the one that got close and past Zoro during that clash, so it gave the impression that Hiryuu Kaen was a close range attack, instead of it being a long range.