Hello Aarohi,
This is happening because the fm ALM_ME_TIME_CONF_CREATE_2 is throwing a warning message (for CNF Orders) not an error message. However, you can arrange for an error message through implicit enhancement at Line2 of the function source code of this fm as shown below. This will throw error message and stop cinfirming, when Orders with CNF status are attempted confirmation through this fm. I am here showing the code used to achieve this through this enhancement.
May like to try. It is a small ABAP job. (You forget about the other inside fm you referred)
Good luck
KJogeswaraRao