This requirement makes no sense to me:

Paths will not necessarily be sequential (characters can be skipped).

Does it mean that points in a path must not be connected with each other? But this 1) contradicts test cases, 2) makes grid representation useless - the kata then is just "find longest lexicographically ordered substring in a string".

After solving it I feel more like "paths must be proper sequential paths with every point adjacent to previous and next ones".