Yes, absolutely they will if you ask. Ask all the questions you want - it's really important to ask and to know exactly what you will be getting if you stay at Prep and what you will be getting at Senior at either 11 or 13.
If you are concerned the standard expected might differ, ask about that too. Schools are used to propspective parents who are considering spending well over £100k asking lots of questions to be sure about what they are 'buying'. The more precise questions you ask, the more specific and useful information you will get.
Ask about no.s applying and no of places offered at 11 and 13.
Ask if the school prefers to admit at 11 or 13 and what they see as the advantages or disadvantages of each point of entry,
Ask if there are any changes in these patterns.
If you have both options within one school, assuming the entry process is similar and undertaken in Yr6 ready for either Yr7 or 9 entry, it will really come down to if you prefer your DC to have 2 further years in the smaller environment of a Prep school where they can be 'big fish in a small pond' or whether you think they will benefit from moving at 11 and being in the Senior school from the beginning, being a 'small fish in a big pond' for a while. There's no right answer and people choose differently, although for day schools the tide is defined ty moving fairly strongly towards 11+ entry. It is different for schools which are boarding, but I don't get the sense you are looking at boarding.
A further thing to look at for the senior school is if a 13+ intake is still being kept open, just to keep one or 2 feeder Preps which go to 13 happy. Quite a few seniors have dropped their 13+ entry altogether or reduced it hugely. This isn't always evident and not told to you by your Prep. Even if your child is at a Prep where a decent proportion stay until 13, especially if they then go onto several different senior schools, it can still emerge that your child is one of only 10 joining the senior school at 13 and over 100 or 150 joined at 11.
So no wrong or right answer, but definitely good to go into whatever you choose with full knowledge about the senior situation and also what the Prep situation for yr 7 and 8 is. Best of luck deciding, and always interesting to know what people finally decide, if you want to update us when you do decide.