its true, my vet gave me a shipped eggs cheat sheet ...they posted it over on the easter egg thread, the same advise is on a redwood incubator web site..the eggs need to sit and rest it isnt so much rough handeling as it isthe 30 thousand ft unpressurised un heated plane ride..like when your ears want to pop that same pressure they beleive detaches the air cell...the fresher the egg the better..the ones that have developed to a point can have DNA scrambled from pressure and cold of the flight..alowing them sit and rest some are able to recover but may quit later on if enough damage.
sitting still in the incubator for up to 7 days allows the embryo to get off to a good start and heal air cell...some they want to sit for up to 10 days....unfortunatly the egg turner does not have a low switch it only tilts, all the way to one side then the other , that can cause problems due to a very sloppy air cell can heal in an odd shape just makes zipping more difficult at hatch time..those are set in ICU unit area of bator in case you need to intervien..you can just raise up one side of the bator just a litttle with a small peice of wood or whatever then switch sides so that you are still moving the embro, just not at such a hard degree that will allow air cell to heal in a good shape.after 6 or 7 days you can just turn the turner right on..
it depends on what region you live in if its really dry you might need to add a little, in styrofoam incubators , they are notorious for drowning chicks..they only add a teaspoon of water then let that go completly dry for 48 hrs ...in styro bators you might not want add any water .just keep watching your air cells..adjust according to that..mine runs between 20 - 30%.. my nephew in england due to thier humid climate never adds water to his incubator..different than here in US, but then they tend to start to beef up humidity around day 16 - 17th to prepare for lockdown,
always hatch shipped eggs in cut down cartons fat eand up.