It doesn't seem to say this - there's quite a nuanced discussion about whether or not it was a slur during that time period[1]:

> The term redskin underwent pejoration through the 19th to early 20th centuries and in contemporary dictionaries of American English it is labeled as offensive, disparaging, or insulting..

> Documents from the colonial period indicate that the use of "red" as an identifier by Native Americans for themselves emerged in the context of Indian-European diplomacy in the southeastern region of North America, before later being adopted by Europeans and becoming a generic label for all Native Americans....

> In the debate over the meaning of the word "redskin", team supporters frequently cite a paper by Ives Goddard, a Smithsonian Institution senior linguist and curator emeritus, who asserts that the term was a direct translation of words used by Native Americans to refer to themselves and was benign in its original meaning ...

> Sociologist James V. Fenelon makes a more explicit statement that Goddard's article is poor scholarship, given that the conclusion of the origin and usage by Natives as "entirely benign" is divorced from the socio-historical realities of hostility and racism from which it emerged.

I think your summary saying the "status in the 17th and 18th century is a bit less clear" is fair, but I think the Wikipeida article outlines that lack of clarity too.

[1] https://en.wikipedia.org/wiki/Washington_Redskins_name_contr...