Not specific to any engine applications in particular but depending on what GM had on hand the over the counter and/or warranty replacement engines were sometimes supplied in CE or suffixed applications..
Consider the genuine Suffixed but non Vin stamped Corvette blocks/engines that are floating around as an example..
On CE's w/ Vin stamps, not that they often/ever did it but wasn't the General's policy instructions to the dealer installing a warranty unit to stamp the Vin into the replacement unit?.
~ Pete