This is nonsense.
The evolutions of the progress flag have been about inclusion of parts of the LGBT+ community that have tended to be more marginalised within the community.
That is why the black and brown stripes were added: not because anyone things being a person of colour makes someone queer, but because LGBT+ people of colour have experienced marginalisation within the LGBT+ community. The same of trans people. The same of LGBT+ disabled people.
I have not seen any, even highly academic, attempt to conflate being disabled (in general, irrespective of sexual or gender identity) and being queer.
The only actual academic discussion I have seen on this is the overlap between disability theory and queer theory, and some of the common experiences of disabled people and queer people (e.g. higher rates of violence, discrimination, homelessness etc). But saying that 'Group X has some experiences in common with Group Y' is not the same as saying 'Group X is therefore part of Group Y'.
So back to the original point - this flag is nothing to do with straight disabled people.