Germany aren't considering the same plan. There was talk of Germany processing offshore, but successful asylum seekers would still go to Germany, which would be legal. It's also something that Labour have said they'd consider.
The Rwanda plan, even over the full five years of the trial, was expected to take just a few thousand (and potentially just 1000), so most refugees would still stay in the UK. Less a deterrent and more another small risk, alongside all the other risks people take to get to the UK.
Israel had a similar (but not the same) arrangement with Rwanda a few years ago. They sent a few thousand refugees, but very few actually stayed in the country. Almost none could be tracked down in Rwanda, but a lot were found in Europe. Remember, that once you get refugee status, there may be restrictions on travel, but you're not a prisoner. If they wanted to come to the UK, they'd almost certainly try again.