Low level LP user...against a very low level inverted player as I was less than a year into picking up the game. I had trouble with 1500 rated inverted players but I could easily 3-0 this 1700 rated inverted/LP penholder. That's what familiarity with LP can bring you.
I mean how often do those national team members play against LP, particularly those who aren't choppers? Low and short and still topspin, wouldn't a 2300+ rated player be able to banana flick it to hell if he can react fast enough to it, which he should if he's familiar with LP receives? What weird spin can legal LPs even generate these days? There's a reason the top choppers all use SPs now. SPs actually give me more trouble because on some shots they can generate just as much spin as inverted (pushes, serves), on some much less (loops), and on some completely dead (some blocks).
LPs can directly sideswipe or attack short serves to extreme angles (I know how easy it is because I played LPs with my offhand a while back) or short push them, so it's not as easy as saying "just banana flick it to hell". Also a short push to the extreme wide FH or BH is not so easily banana flicked lol.
If you serve long you run the real risk of getting looped bad directly. Also LPs are able to do spin variation between full reversal to no reversal - if you see for eg Joo Se Hyuk chopping a backspin serve it often also comes back with backspin despite the stroke being done by LPs - have you thought why? And even LP serves can have moderate backspin - it's not always no spin, and if they're good at disguising it it's also a nightmare, because the same stroke with inverted will produce heavy sidebackspin or sidetopspin but those are non-existent on the ball - your mind starts to play tricks on you and it's incredibly easy to miss the ball this way because you will subconsciously approach the ball like it contains sidespin.
But by far the worst thing that LPs grant is close to immunity to spin variation and ease of dealing with short serves. So say if the penholder has very good serves that you'll make mistakes on, and then when it comes to you serving, he doesn't even need to read your serves properly because the LP can simply handle it.
I posted a few videos of examples of high level LP/inverted penholders which can give you an idea of what's possible.
But what I'm imagining (there is no such player these days but technically nothing is stopping someone to play like that) - is to combine the LP/antispin game of someone like Luka Mladenovic / Zhou Xintong, with someone with the attacking capabilities like Ryu Seung Min or Ma Lin. Now you can see when a lot of players play against Luka, when he chopblocks the loop short they are pretty much forced to push the ball back - and his FH loop is too weak to capitalize on it. But with guys like Ryu or Ma Lin - this would be just be easy fodder for them - these are the balls that they would enjoy loopkilling against all day long without mistakes lol. And it also solves some of the weaknesses of traditional penhold. For e.g. if someone serves heavy sidetopspin to them they can still keep it short using the LPs then keep the game at short-short-massive 3rd ball loopkill mode. Or if the chiquita happy crowd comes in they can sidespin chopblock the chiquita to some weird sidespin abomination, and then loopkill the push.
There are amateurs in China who play like that who already punch way above their league in terms of results - but none of them have the professional training needed to compete at an even higher level (for e.g. the fundamentals, footwork, FH loop, short game, etc...)