Projection pushdown doesn't work in temporal(lookup) join

sql 1: 
|SELECT T.*, D.id
|FROM MyTable AS T
|JOIN LookupTable FOR SYSTEM_TIME AS OF T.proctime AS D
|ON T.a = D.id

optmized plan:
Calc(select=[a, b, c, PROCTIME_MATERIALIZE(proctime) AS proctime, rowtime, id])
+- LookupJoin(table=[default_catalog.default_database.LookupTable], joinType=[InnerJoin], async=[false], lookup=[id=a], select=[a, b, c, proctime, rowtime, id, name, age])
   +- DataStreamScan(table=[[default_catalog, default_database, MyTable]], fields=[a, b, c, proctime, rowtime])

sql 2:
|SELECT T.a, D.id
|FROM MyTable AS T
|JOIN LookupTable FOR SYSTEM_TIME AS OF T.proctime AS D
|ON T.a = D.id

optmized plan:
LookupJoin(table=[default_catalog.default_database.LookupTable], joinType=[InnerJoin], async=[false], lookup=[id=a], select=[a, id])
+- Calc(select=[a])
   +- DataStreamScan(table=[[default_catalog, default_database, MyTable]], fields=[a, b, c, proctime, rowtime])