The fallacy lies not in how difficult a wet, long, narrow 7,000 golf course is for an LPGA pro whose carry distance is 230 off the tee and maybe 200 on a good day from the fairway. They're going to have trouble keeping it anywhere close to par under those conditions. Something in the 75-80 range is likely. Stipulated.
The fallacy is saying "Drives it 300 yards" as those he's going to be walking 300 yards up the fairway 14 times a round and dropping the ball a short-iron from the green in a perfect lie. Not any big-hitting 4-handicapper I've ever seen. He's going to get three or four holes where he just "schools" the short-hitting lady pro. Drives it within wedge distance, hits it close and has 10-15 feet for birdie. He'll even make one or two of them if he's lucky.
It's what he does on the 6, 8, 10 holes where he a) does not get 300 yards out of it and b) is not in the fairway. And at least one or two of those 300-yard (potential) drives will be in the deep shit on a tournament setup. And unless he's a serious sandbagger, several of those bad drives (and BTW hitting it that long on most 7,000 yard tournaments setups it doesn't take much error to get screwed for your second shot) are going to be the occasion of an 8 or 9 or 10 on a hole. Assuming we're talking stroke play, our hypothetical lady pro will be tallying pars and bogeys with maybe the odd double somewhere along the line.
So her scorecard looks like a boatload of 4's and 5's with the odd three and a couple 6's. His scorecard looks an even mix of 3's, 4's, 5's, 6's, 7's and 8's with at least one "blow up" hole of 10 or 11 strokes. He can have the round of his life, make four birdies to her zero and still lose by half a dozen strokes. More likely he makes one birdie on a Par 5 (she pars them all) and shoots 85 with at least a couple of "others".