Children being given books that are consistently too hard does put them off,I've seen it time and time again when teaching. With more able readers you need to tweak it and constantly monitor it otherwise they will be turned off.
I had 1 son who was a free reader in rec and 1 in y1,I wouldn't have dreamt of giving either books that were too hard. It was a constant juggling act and I noticed when they were given books too difficult it most certainly did put them off for a while. The free reader in rec loves challenges but I made sure he read books at his level that stretched him (that is different than giving him books far too difficult) as he was ready for them,he is and was an avid reader as a result.
I'm not going by ORT levels at all but by the colour bands they use in school which use a variety of books some real and various other scheme books of which ORT is included. The Usborne books fit in with these levels and are nice looking books. By choice I'd refer to the real books reading list but I don't have it for her level so the next best thing is Usborne that fits in with the colour bands used by her school.
As much as I love real books there is a place for leveling. My dd is fantastic with reading key words she has learnt by sight however she needs practice at reading words with the particular level of phonemes she has learnt.
Oh and if it was left to her she'd be reading the stash of Roald Dahl chapter books she's eagerly wanting to read,she will attempt to read a sentence and give up as they are simply too hard. Once she's had a few months decoding using the phonemes she's learnt I've no doubt she'll get there.
Not sure why I have to justify all this I simply asked for info on Usborne books.