The prayer of Orthodox hesychasm is repeated, often continuously, often synchronised with the breath, and often counted on a knotted wool cord. That makes it structurally comparable to the material this collection files alongside it. It also differs from that material in one respect its own tradition regards as decisive.
The words are meaning-bearing throughout, and Orthodox teaching insists they must be attended to. The standard instruction is to keep the mind in the words, to descend with the mind into the heart, and specifically not to allow the repetition to become mechanical. The technical term for the danger is prelest, spiritual delusion, and generating the sounds without attention is one of the ways into it.
That is precisely the difference between this and a seed syllable. A syllable with no lexical meaning cannot be attended to as meaning; its operation is held to be of another kind entirely. The comparison filed here is a comparison of structure, fixed formula, repeated, in a devotional discipline, and it does not extend to mechanism.
Its wording varies and the variation is accepted. The full form names Jesus Christ, Son of God, and asks mercy on the speaker as a sinner. Shorter forms drop the final clause or reduce to the name alone, and different teachers recommend different lengths at different stages.
The scriptural anchors usually cited are the tax collector's prayer in Luke 18 and the blind man's cry on the road to Jericho, both of which ask for mercy in almost these words.