This "persistent universe" argument holds no water at all when it comes to solo mode. When there is 1 actual player in that universe and everything else is just a simulation for his benefit, then there is no reason to keep that simulation running when it is inconvenient for that one real person.
Besides, it isn't really a universe that works independently of the player anyways. NPCs spawn as a reaction to where the player is and what he does. They don't really have any life outside of their interaction with that one player. There are no bulletin board missions that get done by NPCs before you can do them for example. In solo mode this game is no different to a old fashioned 100% offline game, at least not that I became aware of while playing it.
In "The Elder Scrolls: Oblivion" the NPCs actually did their own thing. They went to places because they had their own reasons apart from interacting with the player and you still could pause that game whenever you wanted and why not?
In this game ("Elite Dangerous") and especially in solo mode you don't have any interaction with the NPCs beyond shooting them or being shot at by them or having to avoid crashing into them during your landings and takeoffs at space ports and those NPCs you do that to/with spawn and despawn depending on you.
I wouldn't believe you or the developers if they would tell me that they actually have their servers calculate what single NPCs are doing when they are not interacting with the player and that for every NPC in every universe populated by a single solo player, because there is absolutely no reason for doing so and it would be a ridiculous waste of calculating power that wouldn't serve any purpose. The only thing that is "persistent" about this universe is prices for goods and those change because of players in the open game mode do, which is the only reason for why you have to play solo mode online, isn't it?
How is "Space stations, hundreds of light years away from the player's current position, which he probably will never visit in solo mode need their prices for bio waste kept up to date so badly that we can't even allow the player to pause the game for a few minutes!" a credible argument against a pause option?
A game that doesn't allow you to pause can just aswell prohibit you from ever shutting it off. That would just be as logical. What is the difference to the game or the game's universe, whether you shut it off for 20 hours each day or whether you pause it for a few minutes? The only effect a pause option would have on "the universe" is a bit of sensible convenience for the player. How can anyone argue against that?
Also, this isn't a realistic simulation in any way, shape or form anyways. This is just a silly game in which space ships fly around without decent navigation systems, in which they mine asteroids with lasers that have a maximum range of 400 or 500 meters at the most and no radar to tell them how far they are away from the asteroids and in which you can't have any communication with a space station without being inside it, except requesting landing, but can get anyone's criminal record instantly just from scanning their ship. You have to land in port to find out what stuff costs at the market like in a medieval sailing ship, but the information whether someone is wanted is instantly available at any point in the whole galaxy? C'mon... Hard to take this seriously and I don't find it very immersive, to be honest. This is as much of a serious simulation as Tetris or Super Mario Brothers.
There really is no credible argument against a pause option in solo mode.