Does Makita multi-tool DTM51 have a real Starlock mount
No
Your multitool does not have a Starlock mount.  But some Starlock blades are compatible nonetheless.
Starlock
Starlock has three types of blades: Starlock regular, Starlock Plus, and Starlock Max.  The latter are more sturdy.

All Starlock blades are 3D-curved; they have a bulge. The three sub-types differ only in the cutouts.

DTM51 is not Starlock
Your Makita DTM51's mount is not curved, so it's not StarLock.

A 'real' Starlock mount has an inverse bulge like this:

And Makita is starting to sell these too.  See the new Starlock Max DTM52.

Compatibility
Your multitool can however accept some Starlock blades when these blades are backwards compatible with 'flat' heads.
For example, cutouts in the shape of Bosch OIS (Oscillating multitool Interface System) may be present.
Typically, Starlock Plus or Max blades will not have OIS cutouts because they support larger forces for which Starlock was developed.