I travelled to Caen and Rouen by train from Paris easily for than once to see the Bayeux tapestry. Cherbourg would be out of the way. Unless they have dramatically redesigned train transportation in this region things should not have changed in the intervening years. I followed this line three times to get to my destination.
I think the point that the person who gave the OP the information was trying to make, was that not all the Intercites trains on the line from Paris to Bayeux and Cherbourg run all the way to Cherbourg. Some stop short at Caen.
The timetable for the line up to the end of the year is in the link below and you can see that pretty much every second train finishes at Caen, meaning you have to change there to go on to Bayeux. Not a huge problem, but obviously the trains that run all the way to Cherbourg are more convenient.
The Gare St Lazare has screens that list the trains and platforms (voie or quai) for arrivals and departures. Find the platform for the time and train number on the screen that is shown on your ticket. The train number is for scheduling purposes; it will not be on the train.
You should check on
To see the details of trains. It wil give the time the journey takes and if it is direct or needs a change. The train that has the timing for you might need a change at Caen.
Use Bayeux as the destination station in www.trainline.eu. As cpmac says in post #9, take the train with the best timing for you. It is not a big deal to change trains