FMC "flex" isn't allowed in concrete. In 362.10 ENT (smurf) is allowed to be embedded in concrete, so I think it would OK, but the inspector could have issue with meaning of "embedded" with such shallow cover, which could be up to interpretation of "similar finish" by AHJ.
NEC 300.4(F) Cables and Raceways Installed in Shallow Grooves.
Cable or raceway-type wiring methods installed in a groove, to be covered by wallboard, siding, paneling, carpeting, or similar
finish, shall be protected by 1.6 mm (1∕16 in.) thick steel plate, sleeve, or equivalent or by not
less than 32-mm (11∕4-in.) free space for the full length of the groove in which the cable or raceway
Exception No. 1:
Steel plates, sleeves, or the equivalent shall not be required to protect rigid
metal conduit, intermediate metal conduit, rigid nonmetallic conduit,
or electrical metallic tubing.
Exception No. 2: A listed and marked steel
plate less than 1.6 mm (1∕16 in.) thick that provides
equal or better protection against nail or screw penetration shall be permitted.