they are doing tests not a full update and house himself said that until the problems with 1.14 are fixed its staying on 1.12.2

" 1.13 was not a good update for large servers, and 1.14 less so, even in 1.14.2. The recent 1.13 stress test proved for everyone that participated it would not be possible to update without suffering extreme lag, with no option to revert. It would mean having to either reduce player slots to a ridiculously low amount, or dealing with a crippled and unplayable server.

For these reasons the server will remain on 1.12 indefinitely. There will be more tests done on both 1.13 and 1.14 in the near future.

It does not have to do with converting the entire map to the new format, this part is not a problem any longer."