You simply stated training a muscle twice a week is the best. I was assuming you were talking about upper/body, classic splits etc. which has you in the gym a lot more than 2x week. Everything depends on how you group your muscles and how you workout. If you are doing a full body workout twice a week that's one thing. If you are trying to hit your muscle groups twice a week but are doing a lower/upper split that means you have to be in the gym 4 days a week. Hypertrophy specific training has you in the gym doing a full body workout 3 times a week. Saying that "science" says training a muscle twice a week is the best is utter horseshit and has absolutely no relevance to real world training.
nope you are wrong.
protein synthesis after a workout stays raised in that muscle group for 48-72 hours,there is evidence that the cns takes 72 hours to fully recover. also meta studies show that working out twice a week produces the same muscle mass as working out three times per week, but more strength gains.
now that leaves us with the optimum being 2 full body workouts a week - so personally if i were to workout twice a week each workout would look like this:
3-5 sets of 5-8 deadlift
3-5 sets of 5-8 rows (each set superseted with bench)
3-5 sets of 5-8 bench (see above)
3-5 sets of 5-8 squat
i'd eat everything in sight an our before and immediatly after, or use shakes pre/post workout.