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There are references to verification efforts on the relevant Wiki page under "Debate":
https://en.wikipedia.org/wiki/Fajada_Butte#Debate
[quoting:]

There are several issues surrounding this site. One is when the two spirals were pecked into the walls, some scholars suggesting it "postdates the height of the Chaco tradition. Another is its importance. Although other solar observatories constructed by the Pueblo people predict solar events by the movement of the light over a period of time, this one does not. It has also been suggested that it was not built but that those who made the inscriptions were using a convenient existing fall of rock (Kantner 2004, p.99).

Critics generally agree that the light and shadow phenomena at the site were intended to mark the arrival of the sun at the solstices and equinoxes (Carlson 1987, pp. 86-7; Zeilik 1985, p. S84). There is less agreement on the lunar phenomena; Zeilik found no ethnographic evidence for a concern with the lunar standstill cycle in the historic pueblos (Zeilik 1985, pp. S80-4). He also noted that contemporary pueblo horizon observations achieve greater precision than that possible using the sun-dagger site, leading him to conclude that the Sun Dagger site may have been a sun shrine, but would not have functioned well to regulate the solar calendar (Zeilik 1985, pp. S71, S77–S80).