On my switch with version 1.21.94 with experiments turned on spicificly upcoming creator features the upcoming features are not present in the creative inventory
MCPE-225403
Experimental features turned on but still not present
Resolved
Invalid
1
The "Upcoming Creator Features" toggle is for add-on creators. It has nothing to do with upcoming vanilla game features.
The copper golem features are not available as an experiment in 1.21.94. You will need to wait until 1.21.100.