That’s ironic, when the answer to your question is literally in the blog announcing the PTR, and in lots of stickied threads.
Which you can provide without access to the seasonal theme.
The item changes will come to non-seasonal before Season 22 starts when Patch 2.6.10 is applied to live servers. As non-seasonal heroes will not have access to clones / 4th cube slot, what you’re testing in the first week of the PTR is what non-seasonal heroes will have access to after Patch 2.6.10 gives them the amended items.
Again, as per the announcement blog, the Season 22 theme isn’t due to be implemented until Phase 2 of the PTR on October 8th. So, yes, it’s currently working exactly as intended, i.e. deliberately not yet active.
The fact that the Season 22 them is not yet active is NOT a bug.