ABAP database schema for S/4 HANA 1909

Dear All,

Recently I upgraded some of the systems - from S/4 HANA 1709 to S/4 HANA 1909 FPS02 using SUM 2.0 SP 08.

I see that the schema name remains SAPABAP1 after the upgrade to S/4 HANA1909 - the schema same as in S/4 HANA 1709.

I have another S/4 HANA 1909 system installed (i.e.not upgraded from old version) which has schema name SAPHANADB.

I know that default ABAP schema is SAPHANADB as of SWPM 2.0 SP 01 and this cannot be changed since database schema already exists in the database export as mentioned in 2568783. But, schema SAPABAP1 could be changed (Ref 2362492 - How to Rename Schema in SAP HANA)

I am just curious- why doesn't the upgrade of S/4 HANA 1709 to 1909 change the schema name from SAPABAP1 to SAPHANADB? Doesn't upgrade anyways import new exports for S/4 HANA 1909 version?