BUG Rating from similar IES file

I think it is fine.  Assuming all other things are equal.  Typically when the color temperature gets warmer, the lumen output drops 5-10%.  That would only improve the BUG rating.  So having the BUG value at 5000K is a worst case number.

Sorry.  Do you know the total lumen output of the fixture at each color temperature?  What percentage increase? Enter the IES file into software like this. http://www.visual-3d.com/tools/PhotometricViewer/default.aspx Page 2 and 3 of the output shows the BUG lumen values in each angle range. (LCS Table & LCS Graph)  If the 5000K light is 10% more lumens then add 10% more to each area of output. The permitted output is shown here. https://www.ies.org/wp-content/uploads/2017/03/TM-15-11BUGRatingsAddendum.pdf See if that extra 10% pushed any of the Backlight, Uplight, or Glare into the next higher rating.  Example: Maybe forward light very high (80-90) is 205 lumens.  Add 10% and it is 225.5 lumens.  The maximum for glare G2 is 225 lumens.  So the light would become G3 at 5000K color temp while only a G2 at 3500K.  This would have to be checked at each angle.  The highest glare rating of any angle is the fixture's glare rating. There is software available to automatically increase/decrease the lumens and provide a new BUG rating.  Manufacturers do this all the time.  They test one version of the light and other color temperatures are "scaled" from it.  I don't know what they use or if there are free versions available.