IDT Universe on ECC ....ECC Function Module (FM) shows total 3 FMs (becoz of Internal Tables)

Dear Experts,

When a Function Module is fetched from ECC into IDT Universe,

Each ECC-Function Module (which has internal tables logic in-built in it) ....shows 3 Function Modules in IDT Universe level, as highlighted below

Next, I try to join these function modules in Data Foundation layer (on primary key  "-id"), it throws error, as highlighted below.

Any idea on a Function Module (with internal tables) be leveraged into a IDT universe.

ECC version: 6

BO version: 4.1 SP5

Thanks,

AK