I think there is some semantic goofing around on this issue.
What is reception “in voto” anyway? Say I have perfect contrition, confess to Christ, and He says, unknown to me, “Your sins are forgiven”, well, there’s your proximate matter, form and priestly minister right there. I can rationalise how, in this case, the sacrament can be received essentially “in re” via a votum (maybe I’m wrong in this rationalisation, but whatever): in my “votum” is already implied, in actu, the matter of the sacrament, so that Christ Himself can supply the rest.
But with baptism of desire? By definition nobody’s pouring flowing water onto ones head while saying the Trinitarian formula!
It seems only marginally less nonsensical than receiving the Eucharist in voto (oh, I’m sure some theologian has tried).