Creating a tileset with

tippecanoe -z0 -d32 --no-tile-size-limit --no-feature-limit -f -o foo.mbtiles tippecanoe/ne_10m_admin_0_countries.json

and then running tippecanoe-decode on it shows an extent of 1, not 2^32. Not sure yet whether the precision loss is in the tiles or in the decoding.