Don't verify reginsenc if skew/sum assumption

[christianbean]

[I 220712 07:50:55 specification:164] Expanding with regular_insertion_encoding_right on 
    +-+
    |1|
    +-+
    1: Av(012, 021)
    Assumption 0:
    can count skew components in cells frozenset({(0, 0)})```