1. It is not detected that a file is encoded in UTF-8.
2. If a UTF-8 file has a byte-order mark at the beginning, the first READ DATASET statement reads the byte-order mark into the memory, or, if the system is a non-Uniocde system, reads a '#' into the memory. Other terms
CL_ABAP_FILE_UTILITIES, CHECK_FOR_BOM Reason and Prerequisites
A byte-order mark can be used to indicate that a file is encoded in UTF-8 or UTF-16. For UTF-8, the byte-order mark is the byte sequence EF BB BF. The byte-order mark should not be read into the memory. Solution
https://service.sap.com/sap/support/notes/788449 (SAP Service marketplace login required)
Key words : basis support, support package, method check, became available, dataset statement,