I don’t think you’re entitled to pre-emption rights, particularly since they’ve changed the terms recently. If it helps view the frequent public crowdfunding rounds as your chance at keeping your stake.
For small shareholders pre-emption makes little sense for the shareholder, and zero sense for the company (who as Ian said would spend more organising such a round than they could raise from it). If you have a small stake, it doesn’t really matter what precise percentage of the company you own, and if you have a large stake, there is no way you could or should attempt to keep the same percentage of a much larger pie, you would very quickly end up investing way more of your net worth than is advisable in one risky startup.
I was part of a pre-emption round offered by Monzo earlier in their history. It was immensely frustrating as an investor, because they had to limit each person’s shares to a small pro-rata share, and ended up under-raising as a result. After participating in that I think it would have been far better just to have a larger open round, and I hope Monzo just continue to do regular crowdfunding rounds instead of bothering with pre-emption rounds which are fiddly and ultimately a bit pointless. It’d be nice if they did a crowdfunding each year or something in app as they did the last one, it would be a regular chance for investors to up their investment, and doing it regularly might make it easier perversely, instead of every raise being a one-off.