Ineedanewone your DD and my DD1 are incredibly alike, DD is also a scientist and too bright for school to be much help except getting her extra time in exams. She could desperately do with learning to spell, but nothing in the SEN department is targeted at DC who will get A/B at GCSE. She's a reasonable artist and a brilliant singer, but all fingers and thumbs when faced with a violin.
I'm certain I'm dyslexic too, but back in the dark ages dyslexics were boys who couldn't read, not the cleverest girl in the class, who weirdly couldn't spell.
I knew DD1 was dyslexic from Y1 too, late to talk, didn't crawl and a total blank spot for learning to read even though she knew all her phonic sounds.
In retrospect the real give always are not b&d which she didn't do, but the bizarre ones. L & I confused her for years. Crazy guesses at words when reading or writing and spelling the same word different ways on the same page.
The other thing I do too and non dyslexic DD2 and DH don't is miss words out when reading and substitute words that mean the same, but look totally different.
Eg. Hedge for fence without either being in the picture.
I also paraphrase whole sentences and both types of mistakes drive DD2 nuts. She used to correct my bedtime reading from about 5.
OP is great your DS school are so on the ball, it was the end of Y6, with SATs looming before DD1s teacher twigged, exactly the same week as we had arranged to see an ed Phy.
Why were school so useless. 1) original HT didn't like looking for SENs and she tested DD by letting her choose a book. DD, of course choose interesting non fiction, that she could do.
2) DD1 is very bright to talk to.
3) DD1 does not pick up social cues and is forever getting bullied, school were pretty good at sorting this out, but it was a huge distraction.
4) the HT taught DD2. DD2 was the best reader in that Y2 class and she spells without thinking about it. Teachers ought to realise siblings can be very different and socially they are polar opposites too, but I think it did add to the idea one day DD1 would just catch up.
Please ensure school do keep an eye on your DS and offer support with reading and spelling in primary. Secondary is too late, there is too much else going on.
And don't worry, as I say DD1 will get reasonable results and I have Russell group degree.
As DD1 is often heard to repeat "dyslexic does not mean thick"
In fact I think crap short term memory is very useful, you have to turn science etc into a coherent story, because random facts, like spellings, vanish into the ether.