Showing the GRANTs for a role (or extract DDL) DATA ACCESS right is shown as CREATETAB right. so the CREATAB right might be duplicated and the DATA ACCESS is missing.
Use the following commands to replicate the issue:
db2 "CREATE ROLE IFCDS_SH_ADM"
db2 "GRANT EXPLAIN, BINDADD, CREATE_EXTERNAL_ROUTINE, SQLADM, CREATETAB, DATAACCESS ON DATABASE TO ROLE IFCDS_SH_ADM"
The go to Explorer | Security | Roles and select the IFCDS_SH_ADM role
Switch to Grants tab . DATAACCESS is replaced by CREATETAB.