My thinking is that this would flag up the hosts who thought a 3 am arrival / departure was a reasonable request and then sitters would know not to apply . 
Also for those sitters who plan back to back sits , if they know that they can’t arrive until late afternoon ( because they are coming from another sit ) it’s helpful to know before applying if the host needs you to arrive in the morning - then you won’t waste time by applying.
We have had several sits where the host’s expectation was that a sitter could arrive early morning- but this expectation wasn’t stated in the listing and we had maybe a four or five hour drive to get to the location .
The tick boxes could help set expectations from the outset and where the host hasn’t made plans it can be sorted later .