No, you have to select it before you can move on to checkout abnd you have to buy ticket and travel at same time. I tried any trick I knew to then remove the travel and just chek out the ticket but no surprise it wouldn't let me.
A lot of people from the same household will be sharing cars, but you had to book a space each so I reckon half won't actually be used, and it is just a way to ensure the expensive trains and coaches sell out.
What happens if two people turn up in a car, do they get refused? Also the LFD if positive there has been nothing from the club to say money is refunded, someone being told on BM is worse than hearsay and they will probably try to hide behind their 7 day returns policy like when Mönchengladbach was rearranged at 20 hrs notice, and in the end had a ring up and beg policy, but the club won't let fans know about refunds being possible by publishing any info.