There will be a break in and adjustment period with any new mattress over the course of the first few weeks (see post #3 here) and “comfort” is also subjective so it’s not unusual that a mattress that feels similar to another one for some people will feel different for others.
More importantly though I would read the warning posted here because the difference in the layering and some of their other ongoing issues would certainly be a cause for concern.
Foundations aren’t normally included in a return policy but your foundation would be suitable for use with any other memory foam mattress. A credit card chargeback for the foundation may not be approved since it was delivered and their return policy states that it doesn’t include foundations.
Thanks for sharing your experience … I appreciate it (although they are no longer a member of this site).