Proinnsias,
Scott is right, and unfortunately it is an Oracle restriction. And, unless all of your non-prod database storage was Exadata, dNFS-mounted ZFSSA, or FC or iSCSI-mounted Pillar Axiom, this was an issue you are already dealing with today.
But, I do want to highlight even with uncompressing the HCC tables, the data is still filtered, compressed, and de-duped inside of Delphix. Instead of 10X storage savings of some tables with HCC, you get a 10X storage savings of the whole database! Multiply that by however many copies of that production database exist across your whole estate, and the savings are even more impressive.
Also, with Delphix, our compression technology does not get in the way of what you want to do with your data. Oracle specifically says HCC is not for OLTP databases, and to use OLTP compression (a type of AC) for those use cases. Delphix doesn't place any such restrictions on your data.
I also want to point out that this is just a lockin with HCC. Oracle does not have these restrictions with AC, if you didn't want to fully decompress that database.
I just wanted to provide some additional food for thought. Hope this helps.