Every rating system measures the players registered in its pool and the number is not designed to convert to another pool just by looking at the number. Until you have a group of players who havs ratings in both systems, it is hard to measure objectively the playing strength with conversion. Kids (because they are usually new to the playing level their rating describes, something similar applies to rapidly improving adults) also have more gaps in their game, but this also means that that they look better and worse vs specific styles. Unless you know a few players with TTRs in Austria who have also played in the USA, any conversion is subject to personal bias because watching a player struggle often underestimates what they do well and overestimates what they do badly. I remember someone watching me miss a lot of long serves loops into the net when trying to loop them and instead of concluding that the serve was deceptively heavy, the conclusion was that I didn't know how to loop long serves. Usually having seen someone whose strength you objectively know play an opponent can help you better appreciate what is going on.
If the kid is supposedly 1250 in your system, then your system is very different from the TTR system in Germany. Even from where I sit, the kid executed a lot of good pushes on backspin serves, something players stronger than him don't do so well. He also opened aggressively with the forehand when rhe opponent pushed long. Off the bounce countertopspin vs an opening loop is something I have never seen you do, yet this
@KTableTennis competently executed this shot on a few points with his forehand. Might have been luck but he did it at least.
That his backhand and overall approach to returning hook sidespin serves with a topspin element, especially when served deceptively to the short forehand, needs improvement is no guarantee that the struggles were not about trying to read a good serve vs just being a bad serve returner. But these are all things you get a better impression of when you watch multiple matches. I have played pros whose backhand is a weakness for their level but when I play them, I cannot block their shots (many people who say Quadri's backhand is weak would never beat him in a backhand match).
I say all this as someone who has watched a decade of people play "guess the rating" and come up with laughably bad estimates based on overestimating some things and underestimating others. It isn't easy to tell game reading skills and anticipation from watching a match, but they are probably the biggest rating determinants and are why you need to watch an opponent play someone you know to often appreciate their true strength.
My feeling watching him is that his playing against you would be a competitive match. Your rating estimate implies you do not believe this is the case. That is why absent of actual matches or data, such statements are broadly unhelpful.
