When William Paul wrote the first edition of 'The Rose Garden' in 1848, he reviewed more than 100 Teas, as well as Noisettes, Chinas and Bourbons. I think it's incorrect to say that 15 years later, he didn't know how to grow Tea Roses in England. He grew them under glass and out of doors, and his descriptions show that he's familiar with which ones are hardier and which are "uncertain" out of doors.

A better argument against my theory might be that he just didn't like 'CdL' for aesthetic reasons, or perhaps he originally had a weak clone. I'm not sure how many of the later editions of the book were done under his close supervision, but later editions do have a description of 'CdL' as simply being "salmon-pink". He dropped the "second-rate" part of the description, but it does seem as if he sincerely had a change of heart about her merits, he'd have added something to reflect that.

In the 1870's and 1880's there was a mania for declaring roses synonymous that were demonstrably different, but were the same for the purposes of rose exhibitions, and that could be why two different cupped, salmon-pink Tea Roses were said to be the same. Saying roses were synonymous back then did not mean that either rose was an imposter.

At any rate, this isn't a theory I'm anxious to fight for. My only point, really, is that the idea that 'DdB' must be a re-named 'CdL' isn't an airtight case. It seems just as likely that there were two different salmon-pink roses confused in commerce in the 1870's, and that the rose called 'Duchesse de Brabant' was the better rose, and the original 'Comtesse de Labarthe' is long gone, having been replaced in commerce not long after she was first introduced.