A few cycling rags seemed to have been reporting this in a negative way.* It’s probably not good train etiquette, even on an empty carriage. But hardly crime of the century. It’s a bloke on a train with cumbersome (and slightly grubby) luggage. Nothing more. And most trains have dismal storage space for bikes, and in my experience it’s usually where everyone is getting off and on…No way I’d want to leave an expensive bike there. It’s not difficult to understand the thought processes behind it.
*Disclaimer: this may not be true, as I never read the actual articles.