No, that isn't a copying error, but a taste of what might have been if a composer hadn't made friends with a trombonist. That high, lonely trombone solos should appear in Ravel's music is surprising when you consider that the French didn't take to the alto trombone (or the bass for that matter) until relatively recently. Composers were similarly conservative; there is little in Franck, Saint-Saens or Debussy that is more adventurous than the things Berlioz dreamt up for the instrument. After the turn of the century, when Ragtime became popular, the odd glissando appears in serious music (as at the end of Debussy's Ibéria). But that is as far as innovation goes.
Everything changed in 1917. That year America declared war on Germany and before long, jazz musicians had arrived in Paris with the troops. Their impact on musical life was considerable and jazz elements began creeping into the works of many composers working at the time - Stravinsky, Milhaud and others. Their trombone writing, however, remains for the most part in the middle register (though Stravinsky did add that infernal high glissando to The Firebird in 1919).
Ravel certainly heard a little jazz during these years but did not explore it seriously until he made the acquaintance of a young trombone player called Léo Vauchant in 1924. They met regularly for four years and would discuss jazz in great detail together. This Vauchant was a famous high player: Ravel remarked that most of the time he played an octave higher than anyone else despite having a large bore trombone and asked why. The reply was simply "because I'm more ambitious". (The commonest French instrument at the time was the 1860 Courtois design which had a 0.44 inch bore; in America a 0.54 inch was already common. Presumably Vauchant had obtained his instrument from a visiting American.) The meetings began while Ravel was working under great pressure to finish his opera L'Enfant et les Sortilèges and it is this work which contains his first high solo, in the Dance of the Wedgwood Teapot. Young Vauchant must have made quite an impression!
The two men remained friends until 1928 when Vauchant emigrated to America. Just before he left, Ravel showed him a new piece which was provisionally entitled Boléro. The trombonist looked at the long solo and at once protested that it was much too high, suggesting that the composer transpose the whole piece down a tone. You see, Boléro was originally in D, not C! Fortunately for generations of sweating, nervous first trombonists, Ravel obliged. Léo Vauchant later achieved considerable fame as a Hollywood film arranger. Years after his meetings with Ravel, he complained at the stilted approach of classical musicians to the solos in Boléro. Ravel had despaired of writing down all the inflexions which a jazz player would put into his melody and at Vauchant's suggestion eventually left it with hardly any expression marks at all, simply marking the solo sostenuto. "After all, the players will know what to do". Alas, in many orchestras they don't, or are inhibited from trying by the fact that it is such a notorious solo. Most people are familiar with the po-faced rendition the tune often receives. Maybe we would all find it easier to relax with the tune if we bore it in mind that it might have been harder - a whole tone harder!