Building on what @Peter Bartholomew has already done, this in L3 copied down:
=LET(n, QUOTIENT(COUNTA(GridPointTbl[@]), 2),
k, SEQUENCE(n, 2),
list, INDEX(GridPointTbl[@], k),
distinct, UNIQUE(list),
unique, UNIQUE(list, , 1),
na, ROWS(distinct),
nb, ROWS(unique),
r, {1,1} * SEQUENCE(na + nb)...