I take it from your note that you think Subledger Level Reporting Currency will only display subledger transactions (not GL transaction). That is wrong.
Subledger Level Reporting Currency does not mean that only subledger data will be replicated over to the reporting currency ledger and not the GL data from the primary ledger. (I have emphasized this point in the videos)
Subledger Level Reporting Currency means all data, including subledger and GL, will be availble in the reporting currency ledger. However subledger accounting will be available in the reporting currency as soon as it is created by SLA module (rather than when it is posted in GL). Also drill down to subledger would be availble from the subledger level reporting currency.