When 4-point Calvinists like David Pointer attack special redemption because (according to them) it makes God insincere when he offers the gospel to the unredeemed, 5-point Calvinists typically counter that, by parity of logic, election also makes God insincere, yet 4-point Calvinists continue to affirm election.
But that’s not the only doctrine in the remaining four points that’s problematic for 4-point Calvinists. 5-point Calvinists could also raise a parallel objection with respect to perseverance.
If the offer of the gospel is a divine promise, then the corollary of a divine promise is a divine threat. Consider Scriptural warnings about the dire fate of apostates.
Yet God hasn’t made “provision” for the apostasy of the elect. Apostasy isn’t “available” to the elect. Where the elect are concerned, that’s a counterfactual threat. (I'm using "provision" and "availability" because those are the same categories which Ponter deploys to critique special redemption.)
4-point Calvinists reject special redemption, yet two of the remaining four points which they still affirm stand in tension with their objection to special redemption.