I think the key use case here is that you need to do something on or to the Librem 5 but the application to achieve that, for whatever reason, is unusable or inconvenient on the small screen / without a keyboard.
Yes, a lapdock is ideal for that scenario but few people will want to carry a Librem 5 and a Librem 14 and a lapdock. So wouldn’t be great if the Librem 14 could cover for the lapdock when the lapdock is the ideal solution?