Because water levels are different for pressure canning vs. boiling water canning, one could become confused or forgetful in the moment and mistakenly add the water from the jars to the pressure canning water. It is simply a safeguard to help prevent this.
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Why can’t you pour the water from the jars after warming into the canner?
Because water levels are different for pressure canning vs. boiling water canning, one could become confused or forgetful in the moment and mistakenly add the water from the jars to the pressure canning water. It is simply a safeguard to help prevent this.