Holiday Auto

Posting here because they are based in the UK — Ireland.
Just had a pretty bad experience with Holiday Autos.
From what I’ve now read online it seems like the typical bait and switch that they tend to provide. Booked a reservation that specifically was «model» guaranteed with certain features listed and received a different vehicle without the same features (diesel and didn’t get a diesel car).
Literal language was «Special Offer — We guarantee that the model displayed is the model you will receive at pick-​up.» After the reservation, contacted customer service and was told «unfortunately, we cannot guarantee a specific make or model within your selected car category. This is why we always specify that the car displayed is the most common example of the car group and that you will receive a similar car within the category.»
Would someone please tell me what «guarantee» and «model displayed» means when I did not receive the model received and then was told «we cannot guarantee a specific make or model?»