Since you mentioned Greece as a potential private trip, I can relay my experience, not in going on the private trip, but just trying to book it.
In May 2022 was it? when 2023 ABD trips were released, the week of release I believe, I asked our
travel agent to please check on a private Greece ABD for my family of four. (We wanted to see if we could begin the trip on a date of our choosing in 2023.)
A week after my request to the TA I emailed her for an update, but she had no further info about the private Greece trip.
Some time passed with no communication from the TA, again I emailed, & she responded that the vendors ABD worked with in Greece were not responding to ABD’s requests for scheduling.
In July, about eight weeks after our initial request on the private Greece, we still had no answer as to whether or not this trip was possible. The TA said she had no new information; to us, the lack of communication was bewildering.
We decided on a different trip altogether, a traditional group one, which we booked for 2023.
Maybe I wasn’t patient enough, but I think eight weeks was long enough to see if it were possible to even go.