I don't own this light but I have a few D25As and I do some output/runtime testing with a lightbox. I find ET and 47s to be using US-ANSI specs like my Malkoff, HDS, and from what I've followed, Surefire too. My samples from Zebralight, Armytek, and Thrunite (later V2s), seem to be on a significantly more liberal set of standards, certainly closer to Selfbuilt's lumen scale. You can see this in SB's tests of ETs D25 series, and the 47s Quarks and Penlight - he finds these lights output to be in the
40-50% "understated" by his lumen scale. Btw, SB does not make any claims as to ANSI lumen accuracy, just "relative accuracy," with which I agree.
In another independent example, this output runtime graph (on a Fenix lumen scale) shows the ZL SC52 108 lm mode against the D25A 75 lm mode (nearly identical beige and green lines, I had the same results):
Selfbuilt's result: 120lms x 2.5hrs = 300 lm-hrs
Zebralight spec: 108lms x 3hrs = 324 lm-hrs
Eagletac spec: 75lms x 2.5hrs = 188 lm-hrs
Certain manufacturers claiming "ANSI-FL1" standard is meaningless.... everyone is still basically free to do as they please. If you want to compare specs between lights, make sure you use the proper "adjustment" factors, and Selfbuilt's reviews can be a good proxy, if you don't have the equipment or patience to test them yourself. Bottom line - depending upon which manufacturers/lights you are comparing to, you might need to bump the D25 lumen-hour specs up by ~50%.