Most of the argument against machines is usually based around the (1)unnatural movements that machines lock you into and (2)the lack of activity in the "stabilizing muscles" that free weights would stimulate if balance was required. The locked in "problem" will come with any movement done on a machine and I don't think it's that big of a deal when intelligently incorporated into a well thought out program that incorporates free movement. To me it can be used to your advantage sometimes.
Now the second problem is much bigger. Proprioception loosely defined is the sense of where your body is in space. You get that sense along with equilibrium, balance and spacial awareness from a combination of a bunch of things, things like the sensors in your inner ears, visual input, tactile signals (what you are touching) and more specifically to Proprioception - from Proprioceptors which are receptors/sensors in your muscles and tendons. All that shit sends signals to your brain to interpret at approximately a zillion times per second.
When you are locked into a piece of equipment with a substantial portion of your body having contact with the machine this becomes less important because a so much larger part of that feedback becomes fairly constant. Bench, Leg Press, extensions, that cool preacher curl machine you love so much etc.
On the other hand for athletic (cause the word functional picks me sometimes) motion this stuff is most important when you are somewhat upright and requiring some balance with the importance being amplified if you are on your feet and those systems are seeing constant change and adjusting. So Skwatz, deads, standing OHP etc.
So what you loose by doing those on your feet exercises on a machine is not just the appropriate activation of those stabilizing muscles which are so important to prevent muscular imbalances and maximize efficiency. You are also messing up the whole Proprioception feed back system because you are essentially sending it some inaccurate sort of non reality based bullshit to figure out - in essence you are training your body to do it wrong. Then you get in a real life situation like lifting a heavy box above your head, throwing a check, jumping down off your bunkbed or popping up off the couch when the pizza guy rings and you pull a hammy or fuck up your lower back cause your shit is out of wack jack. And it might be really hard to notice any of these drawbacks until you get hurt.
I've noticed that in the last few (?) years most of the new Smith machines at those types of foofy gyms have that angled bar path. I grudgingly will admit that there may be some advantages to that in some specific movements but generally it pisses me off. WTF was wrong with a perpendicular line of travel? It's natural, gravity pulls shit straight down. Your body can understand that better.
Bottom line TLDR- A few months of it won't mess you up too bad because you already have thousands of "real" reps in just make sure you include a healthy dose of natural movements in your life whether that be in the gym or outside of it.
Edit - 'I'm on PCT so I'm just trying to maintain' Nothing personal and I know that's not exactly what you said but Fuck that shit! That's one of the most common sins of the Juicehead imo, such a waste...
