Probation used properly, in both directions

It is also the new person deciding.

Probation periods are treated as an assessment of the employee and are equally the period in which the employee decides whether to stay. Organisations use the first framing exclusively, which means nobody asks the new person what is not working while it can still be fixed.

A structured conversation partway through, asking what has surprised them, what is harder than expected and what they were told that turned out not to be accurate, produces information available at no other time. New people can see the organisation clearly for a few months and then stop being able to.

It is also the moment to correct a mismatch honestly. Where the fit is wrong, saying so early is better for both parties than allowing it to run, and it is considerably easier to do within a probation period than afterwards.

Employment law around probation, notice and termination differs substantially by jurisdiction and by the applicable instrument, and any decision to end an employment should be taken against the actual requirements rather than against an assumption that probation removes obligations.

It is worth adding that the first real task should be chosen for its visibility as well as its difficulty. Somebody who completes something other people can see in the first fortnight has established themselves in the team, which changes how every subsequent interaction goes and is worth engineering deliberately.