A concentrated monk discerns things as they actually are?
Develop concentration, monks. A concentrated monk discerns things as they actually are present.
Samādhiṃ, bhikkhave, bhāvetha. Samāhito, bhikkhave, bhikkhu yathābhūtaṃ pajānāti

Seeing things (pajānāti) is the terrority of wisdom (panna indriya), similar to seeing the signs, traffic, bends, dangers &amp; safety in a road while driving a motor car in the rain.
Concentration is the mind undistracted &amp; clear; similar to the clear windscreen of a car in the rain.
Mindfulness remembers to keep the mind undistracted &amp; clear; similar to the windscreen wipers of a car constantly moving back &amp; forth, keeping water off the windscreen of a motor car in the rain.
Mindfulness does not engage in 'seeing things'. The word 'sati' ('mindfulness') means 'to remember'; 'to bring to &amp; keep in mind' (refer to MN 117).
The false idea that mindfulness 'perceives', 'sees' or is 'bare awareness' is possibly the greatest error in Buddhism, made by many notable mass-market 'teachers', including Ajahn Brahm, Henepola Gunaratana, Bhikkhu Yutadhammo &amp; Joseph Goldstein.
Ajahn Jayasaro provides a correct explanation of mindfulness in this short video.