“standing is also lacking when a litigant attempts to sue to contest governmental action that he claims injures him as a taxpayer”
That’s a rejection of standing for general suits against the government spending our tax dollars, but in this case, we have Joe Biden, who isn’t a member of Congress, who didn’t take a vote from Congress, and therefore has no authority to spend tax money, spending the money. So it’s quite a different situation from the one that resulted in the ruling you are citing.
Even if a law (or executive order, or a bureaucratic regulation) is Unconstitutional, that does not mean that any Tom, Dick or Harry Taxpayer has standing to challenge it.
The PLF understands this.