Absolutely.
Most people from the Middle Ages would have no trouble understanding why Van Eyck painted that lamb as he originally did. The Lamb of God might not be comprehended - nor found acceptable - by them if presented simply as a realistic lamb from a contemporary Flemish barnyard.
It took the high-priced smarties of the Renaissance to "reeducate" us.
This looks like a really interesting website; not completely up yet:
http://legacy.closertovaneyck.be/#home/sub=teaser