It’s definitely been not only possible — before, during and in the years after that Boris Johnson incident — but repeatedly accomplished. Most of the times where I’ve seen it done are during the ESTA era.

Even having a listed US place of birth on a non-US passport doesn’t guarantee that the person is a US citizen — and sometimes even CBP needs a reminder of that. ESTA does require a place of birth.

For years and years during the ESTA era — BoJo’s incident was pre-ESTA — CBP used to even have language on its website noting this possibility of US dual-citizens doing this. CBP eventually scrubbed all such language from its website. Even after that language was removed, it has continued to be done.