'We must not conclude that the Church restricts the uncovenanted mercies of God': what Article 18 does not mean

From the 1834 Bampton Lectures of Richard Laurence (then Archbishop of Cashel), Sermon V, addressing  Articles 10 and 13 in relation to 18, 'Of obtaining eternal Salvation only by the Name of Christ'.  Under the subheading of 'Salvation of Heathens', Laurence insists that these Articles do not exclude those of other faiths from "the uncovenanted mercies of God", again noting (as with Article 9) the generous vision of salvation upheld by Zurich:

But because our Church ascribes not to human virtue, contemplated as independent of Christianity, the power of conciliating divine approbation, we must not hence conclude, that she restricts the uncovenanted mercies of God, withholding salvation from Heathens, upon whom, walking in darkness and the shadow of death, the light of the blessed Gospel has never arisen. Although persuaded "that there is none other name under heaven given to man, in which, and through which, we can receive health and salvation, but only the name of our Lord Jesus Christ";  although rejecting the creed of the Infidel as vain, who, actuated by presumption and pride, treads under foot the Son of God, and deems the blood of the covenant, wherewith he was sanctified, an unholy thing; yet she determines not the case of the Gentile world, or in any way solves a question foreign to her purpose. Indeed the real sentiments of our Reformers upon this point appear to have been different from those which some have imputed to them. For while, like Luther, whose private opinion upon it was nevertheless far from being contracted, they established nothing directly upon the subject, they indirectly seemed to assert, what Zuingle had boldly and publicly taught, that the Kingdom of Heaven is open to Heathens as well as Christians; at least, in the liberal language of the Zuinglians, they held the oblation of Christ upon the cross to be "a perfect redemption, propitiation, and satisfaction, for all the sins of the whole world".

In the Articles, however, immediately under review, they proposed to themselves another object: in these they meant not to launch out into any unnecessary speculations, but to attack in one of its strong holds the pride of scholastical sophistry; to oppose the presumptuous doctrine of congruous merit. 

In a footnote, Laurence expands his account of Lutheran views on this matter:

When the Lutherans withheld from the Heathen world the security derivable from a participation of the Christian Covenant, they never meant to withhold from it (as I have previously remarked in the case of infants) a claim to the uncovenanted mercies of God. They excluded it from the certainty, but not the probability, of salvation.