I can't make any assesment on the quality of the paper as that is far outside my expertise, but as far as I can tell from a quick skim it does indeed make the claim that recommendations for supplements should be significantly increased.

From the abstract:

> The safe upper limit for children can easily be increased to 2,000 IU of vitamin D/day, and for adults, up to 10,000 IU of vitamin D/day has been shown to be safe. The goal of this chapter is to give a broad perspective about vitamin D and to introduce the reader to the vitamin D deficiency pandemic and its insidious consequences on health that will be reviewed in more detail in the ensuing chapters

The full article is available on researchgate[1]. Direct link to PDF [2].

[1] https://www.researchgate.net/publication/226676251_Vitamin_D...

[2] https://www.researchgate.net/profile/Michael-Holick/publicat...

EDIT: I just looked up the author, Michael F. Holick. Apparently he is one the people who identified calcitriol in 1971. I know appeal to authority doesn't prove anything, but it might be prudent to at least consider his findings.