@Matt ******
if you're from one of the 51 countries that can get a 30 day visa exempt on entry then yes you get a 30 day visa exempt entry stamp.
Whether you stay over night or can come straight back is totally up to the border you're crossing at Cambodia, the RULE is clearly written when you buy a visa on arrival to Cambodia that it says you must stay 24 hours in the country. BUT some borders don't care and others want you to "dontate" to get out earlier.
There just are enough people who have done it yet to have any history, so you're in uncharted territory with most of the advice you're going to be given from before this covid shit show closed the borders 😮