You are right. Changing of the dividend rate of a dividend, just like changing of leverage rate is NOT a corporate action so NO OCC adjustments is required. Options were priced correctly according to the change in leverage rate.
I am glad you convinced yourself on this one.
If the prospectus of an ETF at the start of trading says it's a 2:1 leverage... than that's pretty much a fixed given. Changing that changes the entire product.
If a company pays out 1% dividend (which is determined by the shareholders meetings, not stated in any prospectus) and then changes it to 2% or whatever... due to normal business circumstances... that's what it is... normal business. If they decide to payout 10% because of excessive cash... that's not normal business, so the options specs are changed.
If Velocity decides to change the leverage, which was set in the prospectus (as far as I know)... that's not a normal business practice.
I am glad you've convinced yourself that changing the underlying calculation set within the prospectus is the same as changing a dividend. Good on you, I hope you'll not get yourself caught up in a corporate action one day because of this in-grown believe.