I'm not asking you to speculate. I'm asking you to tell me what "blameless" means. Do you think it means "sinless"?
G273
ἄμεμπτος
amemptos
am'-emp-tos
From G1 (as a negative particle) and a derivative of G3201; irreproachable: - blameless, faultless, unblamable.
G338
ἀναίτιος
anaitios
an-ah'ee-tee-os
From G1 (as a negative particle) and G159 (in the sense of G156); innocent: - blameless, guiltless.
Mat_12:5 Or have ye not read in the law, how that on the sabbath days the priests in the temple profane the sabbath, and are
blameless? G338
Luk_1:6 And they were both
righteous before God, walking in all the commandments and ordinances of the Lord
blameless. G273
Joh 8:7 So when they continued asking him, he lifted up himself, and said unto them, He that is
without sin among you, let him first cast a stone at her.
G361
ἀναμάρτητος
anamartētos
an-am-ar'-tay-tos
From G1 (as a negative particle) and a presumed derivative of G264; sinless: - that is without sin.
They are all very closely related.
John's parents would have made sacrifices for atonement just as the Law instructed them to do and they obeyed by faith in God. So under the Law they were found to be blameless.
But the blood of bulls and goats can never 'take away' sin guilt for justification onto salvation. One has to go beyond the Law to find that justification found only in the blood of the Lamb.