These would be labeled the same (BXn ; where n=the # of BX generations). Since the breeding nomenclature or suffixes are just shorthand for the breeding process used irrespective of sex (in this case backcross), the label is correct. Usually, backcrossing is performed with a targeted female since they best exemplify desirable traits manifest in the most useful form for observation (assuming your goal is consistent exemplary females, it's hard to spot female traits in a male). While female targets for backcrossing is the default assumption, there is no reason why the process couldn't be employed with a male as the target. Since the breeding process itself decides the nomenclature, the BXn label, albeit incomplete information, is still appropriate.
Since the male backcross is not the norm and there is no "law" about breeding shorthand outside of the generally accepted practice, you could develop your own shorthand if you find the gender neutral BXn label insufficient (♂️BXn). If this were to ultimately end up as a seed listing, you could expound on its male-centric process in the description. A full throated "labelling" such as should appear in a seed listing could include all relevant/available info:
Couple ways to convey the fact it is a male BX depending on which component of the label/listing you'd like to expand:
Strain Name Breeding Nomenclature - [Genealogy following FxM order] : Full description sufficient to describe any info not encapsulated in the preceding labels.
Jewels OG Male BX1 (regular)
Jewels OG ♂️BX1
Jewels OG BX1 - [(SFV OG x Jewels OG) x Jewels OG]
Jewels OG BX1: Unlike most backcrosses, this OG was developed using a targeted male for backcrossing in order to...
While the question only related to how one could label a target male BX, I would like to comment on the 'x' between the two columns. Assuming that you'll eventually cross a chosen male from the first BX column with a chosen female from the BX of the second, you would end up with a "true" F1 hybrid. Common usage of F1 hybrid now just means a female from something crossed to a male from something. Its more technical usage involves true-breeding strains creating a new hybrid. The hypothetical multiple backcrossing prior to the first filial crossing (F1) would more closely align with the technical understanding of a hybrid, as each parent is first made to be inbred or true breeding prior to their crossing. This could be performed using different heirlooms since they come to you more-or-less true breeding without the need to BX, but polyhybridized starting stock can benefit from a couple BX generations prior to crossing. The idea of hybrid vigor comes from the injection of "new" genes into what is an inbred line (the more inbred, the more recessives can pop up which subsequently get "washed out" in the F1 hybrid leading to expression of more vigorous traits).