A concentrated monk discerns things as they actually are? Samadhi Sutta
(Concentration)
[Translated from the Pali by Thanissaro Bhikkhu.]
“Develop concentration, monks. A concentrated monk discerns things as they actually are present...

Is this an accurate translation of this part of the sutta? Isn't seeing things as they are mindfulness territory or mindfulness and concentration territory?

My understanding is that a  strongly concentrated monk usually focuses on concepts not actual reality. When one concentrates on reality as it is(reality without concepts) then it's difficult to get strong concentration but when one concentrates on a concept that doesn't move around and is more stable than actual impermanent reality then the concentrated monk can reach those great blissful jhana states. 

Only meditation of reality will lead one to the understanding of reality or panna.

I don't know but it kinda  sounds like this translation is implying that concentration always shows one reality as it actually is but usually, concentration meditation involves one pointed attention on one concept not reality as it is.

The kind of concentration that is usually used for "seeing things as they are" is khanika samadhi or momentary concentration. This kind of concentration is used in Satipathana Vipassana meditation. It's like one pointed concentration only when a distraction comes, the distraction becomes the new focus until the distraction falls then it's back to the original focus that is often the sensation  breath as it happens, moment by moment.
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.