All we know is that Wladimir considered the Bagrations equal to other former reigning dynasties. Im not sure if he had met his future wife by that time and if that may have influenced his decision.
Considering that Nicholas I stipulated the marriage of his daughter Maria to the Duke of Leuchtenberg as equal even though the Beauharnais were not a reigning dynasty and they did not belong to the Bavarian Royal House in spite of being closely related to the Bavarian monarchs.
Nicholas II seems to have considered the Bagrations also a former reigning dynasty so Wladimir may have taken his lead from him.
As for the status of the Infanta's marriage im not sure about the rules in Spain. I believe it required an equal marriage but im not aware of any stipulations on who would decide if the match was equal. Was it the king or the Cortes or just what was generally accepted. I think some of our Spanish posters might be able to help with that part of your question.
I'm surprised by the 1946 union of Infanta Maria de las Mercedes of Spain (1911-1953) and Prince Iraki Bagration of Mukhrani. I've heard conflicting accounts: somebody on this board said that it was dynastic, since the bride had requested the consent of Juan, Count of Barcelona (who by then was the head of the Spanish royal house), who in turn consulted his Romanov cousin, Grand Duke Vladimir Kirillovich of Russia (notwithstanding the fact that his claim to headship of the imperial house was not entirely undisputed). The latter ruled that the Bagrations were a royal house, and hence *equal* to the Bourbons.
But in a private e-mail (name withheld), I was told that Juan was never consulted about the matter. Rather the bride's father, born Prince Ferdinand of Bavaria, consulted Vladimir directly himself, and received the go-ahead for his daughter's marriage.
Yet, Wikipedia (which of course needs to be taken with a grain of salt) states that the union was contracted against the advice of Juan, who refused to recognize it as dynastic.
So it seems that while the good part of European royalty recognized Vladimir's claim to headship of the Romanov imperial dynasty (and hence authority to rule on marriages in accordance with the Fundamental Laws), there have remained question marks and doubts about the exact status of the Bagrations.
In any case, I wanted a clarification of the situation regarding the dynastic status of the marriage.