There is no real discrepancy in the two works.

In a practical treatise, he speaks of religion rather than of philosophy; just as he appears to identify virtue with pleasure, and rather seeks to find the common element of the virtues than to maintain his old paradoxical theses that they are one, or that they are identical with knowledge.

The dialectic and the idea of good, which even Glaucon in the Republic could not understand, would be out of place in a less ideal work.

There may also be a change in his own mind, the purely intellectual aspect of philosophy having a diminishing interest to him in his old age.
Some confusion occurs in the passage in which Plato speaks of the Republic, occasioned by his reference to a third state, which he proposes (D.V.) hereafter to expound.

Like many other thoughts in the Laws, the allusion is obscure from not being worked out.