Yes..that's what I was looking for.
I suspect that there might be some "offbeat" brokers who have created a "workaround" to this.
But, even if there were, they probably have prohibitive commissions, and would be smaller, less known firms.
This has to be the dumbest margin rule out of all of them.
The risk is equal whether you do a "normal" calendar, or a reverse one.
They create this margin under the "assumption" that the long leg WILL expire first, and you WILL be holding a short, naked option.
I know in my case, and probably in the case of any "trader", they would be exiting this trade well before the expiration of any leg.
As long as both legs are open, and in place, the position should be margined as such.
If/when the day comes when the front leg expires, and you are holding 1 short option, THEN the margin should change to reflect that.
This is the way it works with all futures options.
So, ES might be a decent workaround for this.
After a spike in VIX ( a sharp drop in ES), when the IV on ES has spiked as well, this might be a good time to put on a reverse calendar because you get to sell IV that has spiked, and will also benefit from movement away from the current price, which is much more likely after a sharp drop in SP's..
So you have 2 things working for you, and no margin with ES