Marcus Aurelius' campaigns against the Marcomanni and Quadi contradict it
That was a defensive campaign and a punitive/securing the border expedition, the intent never was to conquer that part of Germania
And you'll end up with certain tribes (as happened in the East) who can't compete with the coming powers look south and see a nice anarchy in the middle of some prime land. It's not exactly hard to get across the channel and if you can't expand at home heading abroad to colonize has been a common option for thousands of years.
Which coming powers? Without the anarchy caused by the Roman retreat the island will be relatively stable, probably no Anglo-Saxons and the Picts don't have the occasion to sack Britannia. Also if there is a coming power then you first try to defend your homeland and then you migrate but any coming power that would force you to migrate will probably destroy you before you can migrate
Gifting a large amount of gold or similar valuables, enabling a friendly leader to hire more warriors and so increase his strength, was a common way for rich empires to manage tribes beyond their frontiers. It's not an infallible way, sure, but that doesn't mean it has no effect.
What advantage do the Romans get from this? IMO they wouldn't be that interested in Britannia
Logistics didn't stop the Britons settling in Brittany, or the Saxons and Vikings settling in Britain, and the latter two had to cross larger bodies of water than our hypothetical British tribe would. And if the POD is some time in Claudius' reign, that still leaves a good 350 years or so before any "scramble for Gaul" happens (assuming the Roman Empire falls at around the same time as IOTL), so there's plenty of time for some political consolidation to happen. The trend in Germany was for smaller tribes to coalesce into larger ones, and it's likely a similar process will happen in Britain as well.
Those larger tribes will fight among themselves more than look at the Romans' territory, once the scramble for Gaul happens these tribes will probably be busy fighting among themselves and even if they did decide to go to Gaul I doubt they would be powerful enough to succeed
Honestly, you could completely prevent Rome's conquest of Britannia relatively easily. Just keep Rome's conquest of Germania going.
With Roman military resources tied up in Germania no one's going to give Britannia a second glance and the conquest of Germania is going to be a multi-generational process that will probably take most of the first century AD to pull off.
By the time Germania to the Elbe is fully conquered no one's going to even consider a conquest of Britannia.
A conquest of Germania isn't that difficult, before the Battle of Teutoburg the area was pacified and could be compared to Gaul after Caesar, if the campaigns in Germania continue then the Romans will need only a decade or two to manage to pacify the area, they didn't do OTL because Tiberius was worried about the growing popularity of Germanicus and because doing so would be extremely costly.