A true story that illustrates the problem perfectly. Over 30 years ago I was an RPI and working a train north from London with a colleague on a Sunday afternoon when he came to a young man who had no valid thicket.
In common with normal practice then, I continued checking the train whilst he dealt with the offender. Having finished, I walked back through the train and found my colleague seated opposite the young man, neither of whom were speaking at that time.
I said 'All done mate?' and my colleague replied 'No, I was waiting for you to help check out some details' and he handed me his notebook in which the young man had written down what he had given as 'his' name and address details. I was surprised to see that he had given MY address!!
My colleague knew my address well enough, having visited socially and, needless to say, on this occasion the young man ended up facing prosecution.
He did live in an area of town not far from me and had given what for him were a random street and house number. That humorous incident aside, many people will attempt to give false details and whether it succeeds usually depends on the willingness of the staff to probe legally with questioning in line with the Codes of Practice defined in the Police & Criminal Evidence Act (1984) and the tenacity of the inspector in properly evaluating and acting upon what they have been told.
With good training in interview techniques and some technological assistance available to most RPIs, including body worn video, the fact that a very high percentage of travellers are creatures of habit makes it generally easier to ultimately correctly identify any offender than it used to be. It does however rely on these staff using their abilities and support efficiently.
The final point to remember is that if facilities were available to them, a traveller who has no valid ticket when checked is obliged to give their correct name and address (National Railway Byelaw 23).
I've spent the last 20 years managing prosecutions and can say with some certainty that giving a false name and address in response to a request by rail staff or police with intent to avoid a liability makes this a much more serious matter and almost always results in prosecution. (The Regulation of Railways Act [1889] Section 5.3 (c)).
If and until we have a legal requirement to carry in-date photographic identity documentation, that isn't going to change much. I'm certainly not in favour of such restriction on our freedoms, but really do wish that more staff would complete proper checks so far as practical before completing any reports.