I quoted that verse last week, on this thread or a different one. The sacrifice of the Passover lamb was a remembrance, not an atoning sacrifice.
Those Passover lambs after the first, or initial ones, while still in Egypt. That lamb could be seen as an atoning or "cleansing" sacrifice (before the Tabernacle, or Temple, or even Altar) since the blood of the lamb was put on the doorposts, probably prefiguring the blood sprinkled by the High priest, for the cleansing of the Holy of Holies, etc.
Exodus 12:
7 Then they are to
take some of the blood and put it on the sides and tops of the doorframes of
the houses where they eat the lambs.
Of course, there was a dual purpose--as "a sign" so that they would not be killed (by the final plague):
12 "On that same night I will pass through Egypt and strike down every
firstborn-both men and animals-and I will bring judgment on all the gods
of Egypt. I am the LORD . 13 The blood will be a sign for you on the
houses where you are; and when I see the blood, I will pass over you. No
destructive plague will touch you when I strike Egypt.
They were saved "by the blood of the lamb." Just so, the "blood of Jesus Christ cleanses us from all sin." [1 John 1:7]
DG