Truncate custom table dynamically in PLSQL R12.2.11

Hello,

Currently we are using EXECUTE IMMEDIATE 'TRUNCATE TABLE custom_schema.custom_table_name'; in Oracle R12.1.3.

But we are upgrading our application to Oracle 12.2.11 and i did some online materials that we should not be referring to any custom_schema name before the table_name going forward in Oracle from 12.2. Wihtout using custom_schema in my program, it fails with table or view doesn't exists but if i use custom_schema name it works. Is it safe to use custom_schema for truncating the table in my dynamic query.? will this impact any online patching.?

Because of the volume of the table delete is taking longer time and causing performance issues, so we are using truncate.