As I've already stated repeatedly, I see exclusion of parole completely arbitrary. You could argue that it's not equivalent certainly, but you can't just dismiss it.

All you've said about it before was that you thought it was "splitting hairs" once. What do you suppose we do with probation then? Is there a Soviet purge-era equivalent with a measure we can compare?

we're comparing peak incarceration rate in USS right after the revolution with incarceration in US when its functioning regularly

Well, that's what we sought to compare. Both you and EgoCom claimed stuff like "US incarceration rate is higher than what USSR had during Stalin's purges".

The fact that USSR numbers drop significantly over time while US numbers do not, is what's really key here.

It's hard to have numbers drop a frick ton when you've had no arbitrary purging of ideas that led to gulag-levels of arrests.