They are different, I used Devel::Peek to check:

use Devel::Peek;
# ...
Dump $s1;
Dump $s2;

__END__
SV = PV(0x60003a520) at 0x600078300
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK,UTF8)
  PV = 0x600069210 "m\303\270\303\270se"\0 [UTF8 "m\x{f8}\x{f8}se"]
  CUR = 7
  LEN = 16
SV = PV(0x60003a470) at 0x6000e2960
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0x60016e4d0 "m\370\370se"\0
  CUR = 5
  LEN = 16
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Another way how to check the difference is to use is_utf8() from Encode. Read about the UTF8 flag in the documentation.

use Encode qw{ is_utf8 };
# ...
say 'Same UTF8 flag: ', is_utf8($s1) == is_utf8($s2);
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