With all that being said:
So I guess I ended up agreeing with you, question mark.
EDIT: OMG! Could it be that it was not Kizaru's, but Rayleigh's Haki that made his sword clash with Kizaru's?!!!
When he used Haki to redirect his attack on Zoro, Rayleigh was able to contact his real body, but it didn't nullify the ability (hence the missed explosion). Perhaps Kizaru's "Beam Sword" would normally cut through anything, and only Rayleigh's Haki on his sword prevented it from being vaporized!