Yes, it is a once-bloomer -- but it has a long blooming period.

Modern Roses did not have a parentage for 'Shailer's Provence' up to and including MR XI. MR 12 probably based it on the traditional statement from Rivers in 1837: "it seems to be between the Boursault and Provence rose", which was repeated by later authors. MR12 missed that L'Héritierana was not around for at least 20 years after Shailer's cultivar.
The advantage of HMF is that it is in continuous development as many hitherto unpublished references are added and mistakes are corrected:
The 1851 reference e.g. refers to a statement by Henry Shailer junior himself that 'Shailer's Provence' is a seedling of the Spineless or Virgin's Rose. Already in 1810 Andrews questioned : "It is as yet so little known, that a dwarf variety of the Province is frequently sold for it; a mistake most probably owing to its being common called amongst cultivators Shailer's Province Rose: but it certainly bears most resemblance to the Rosa Indica, and is, as far as we can understand, a hybrid production between the two species".

One confusion which is not yet sorted out:
- In his 1851 article, Henry Shailer lists 'Shailer's Provence' = Rosea gracilis under Moss roses. The latter is listed in HMF as Gracilis (moss).
- The rose in cultivation is however not a moss rose. Andrews states in 1810 that nurserymen sell another dwarf variety as 'Shailer's Provence'. Is that its origin?
- Another listing is for Gracilis (Boursault). This could be identical to 'Shailer's Provence' as mentioned in the 1851 article