These quotes all pertain to dubious papal elections.
But since John XXIII, none of the elections have been contested, and universally accepted by the Church.
Do sedes attempt to construe quotes such as this to mean that, although the entire hierarchy accept a man as pope, nevertheless, individual layman may disagree, withold assent, and separate themselves form him? And if the entire hierarchy finds no irregularity in the election, on what basis can a layman?
That is not correct. It is not just the election, but also what is highlighted in red:
F.X. Wernz, P. Vidal: “Finally they cannot be numbered among the schismatics, who refuse to obey the Roman Pontiff because they
consider his person to be suspect or doubtfully elected on account of rumours in circulation.” (Ius Canonicuм, 7:398, 1943)
Rev Ignatius Szal: “Nor is there any schism if one merely transgress a papal law for the reason that one considers it too difficult, or if one refuses obedience inasmuch as
one suspects the person of the pope or the validity of his ɛƖɛctıon, or if one resists him as the civil head of a state.” (Communication of Catholics with Schismatics, 1948)
De Lugo: “Neither is someone a schismatic for denying his subjection to the Pontiff on the grounds that he has solidly founded [‘probabiliter'] doubts concerning the legitimacy of his ɛƖɛctıon
or his power [refers to Sanchez and Palao].” (Disp., De Virt. Fid. Div., disp xxv, sect iii, nn. 35-8)