I'm sure the fully developed and ready to hatch neonates on your shelf and the ones in the wild experience temps below 22°C whilst waiting for the spring thaw (hence them hatching after just 4 days after you put them in the incubator), but not the developing eggs... during the critical stages of development. The eggs are laid from late September to January, sometimes as late as February. The hatchies in nests laid late in the season will often delay emerging until spring. Incubation temps of nests or the ones on your shelf wouldn't fall below 22° (unless that shelf was one in your refrigerator - or you weren't being aircon smart)
that time of the year and if they happened to over night or in the wee hours of the morning, it wouldn't be for long. The
longicollis eggs wouldn't develop whilst constantly below 22°. The little turtles that over winter however would simply brumate, enter a prolonged period of torpor in the nest.
There is a species of turtle though;
Macrochelodina expansa - Broad shelled turtle that lays its eggs in autumn (March-May) and they experience a diapause - (period of suspended development) over winter and continue to develop when spring arrives hatching after 192 days. Artificially incubated
expansa eggs also must go through this diapause by switching the incubator off entirely for at least 4-6 weeks or they will not hatch if continuously incubated. The record for broad shelled turtles that hadn't emerged from their nest is 664 days, after the eggs were deposited. On day 664 the nest was excavated and all the baby broadies were alive and well, the cap of clay soil sealing their nest had turned as hard as concrete and they couldn't emerge themselves.
Whilst
expansa eggs go through a diapause over winter, this is not the case for
longicollis. Their developing eggs don't over winter, only the ready to emerge hatchies sometimes do.