i think he'd be befuddled but happy if he had improved as you suggest, and he ran a PR after this weird alternation of press then relax. i don't think he's saying i used to run 19, i practice like i'll do 18, but because of this stuff it's 18:55.
to me he's saying he goes foot way off the gas after initially pressing, and in relaxed mode has lost all sense of pace. when he also says, i train real hard, that to me screams, he goes too hard in practice, at what is usually a few days of shorter distance intervals or fartleks or whatever, he doesn't actually work on sorting out a 5k race pace, and so he's stuck on race day with either the gas floored or he eases too far off and runs a slow time.
i had a little bit of trouble with this as a sprinter trying XC, it took some work to get it. as someone who could run a quick quarter i had lively legs relative to distance folks and sometimes would find myself, initially feeling fresh, out with the lead pack, or even in first. and wouldn't pay until late mile 2. it took some work to shift into, ok, here is a pace i can hold for 2-3/4 mi before a sprint finish. and you can't sort that on meet day, which is what it sounds like he tries. you need to have pace sorted and know it by feel before you show up. you then do what you practiced. if what you practiced is jam your foot down on the gas, and you panic and say, crap, i can't do this 3 miles, what is left you practiced?
that's also part of why i said, compete. if you've kind of messed the pacing you can guess what you have in the tank and then try to work to the next guy up, or at least defend your position best you can.
to me it's he works hard in practice but doesn't work on anything specific other than fitness, like, how he's running the race or plan for it much. dial back the effort a smidge and work on hitting intervals you can actually repeat. a pace you can keep. then run to that feel or with guys you know run that pace. you then have something other than panic or over-relaxation polarizations in your brain when the race happens.
to me part of this is when you go through practice but it's not explained "why" you are doing things.