James White, in his first book (one that addressed Roman Catholic soteriology) wrote the following:
Hebrews 2:17 says, "Therefore He had to be made like the brethren in all things, in order that He might become a merciful and faithful high priest in things pertaining to God, to make propitiation for the sins of the people." Here the writer of Hebrews teaches that Jesus' role as high priest was so that he might make propitiation for the sins of the people. This means that Christ's death has atoned for sin. There can be no other propitiation if Christ has already atoned for sin. Sin is not "partially propitiated." It is either forgiven, removed, or it is not. If Christ functions as the High Priest and is the propitiation for a person's sins, then those sins are completely and fully removed. (James R. White, The Fatal Flaw, location 2063 of the kindle edition)
This is more of a problem for Calvinism than other non-Reformed soteriologies. If this is the case, then that means that Christ propitiated the sins of the elect when He died on the cross (per the Reformed interpretation of John 19:30). And yet, in Reformed theology, the sins of an elect person are not propitiated/removed until they are efficaciously drawn.
In reality, Christ is truly the propitiation for the sins of the world (as per 1 John 2:1-2 and other key texts), and is an on-going propitiation, not a past propitiation, as the Greek of Heb 2:17 shows (contra Reformed soteriology), but it is only “actualised” when a person repents and is baptised for the remission of their sins, per Acts 2:38 and other important passages.
As always, in an attempt to “prove” that Calvinism has a high view of a particular doctrine (in this case, the atonement), such ends up showing the internally inconsistent and anti-biblical nature of Calvinism. It truly is “another gospel” (cf. Gal 1:6-9).