I looked at the photometric reports from a couple Waveform models on their website and the R9 (saturated red rendering) was in the 90s for both with tint almost exactly on the blackbody line. The 2700K did have a bit worse R9 than the 4000K so I could imagine it doesn't look exactly like an incandescent.
I mean I hate to be like "vibes", but, kinda vibes. There's just something about the light coming out of the Waveform LED I have in one lamp in my living room versus the incandescent I have on the other side of the room. Definitely not a scientific take!
I did at one point randomly put the LED in different configurations when I first got it and my wife was able to pick out which lamp had the LED in it every time. They just have a different feel, even if the temperature rating is around the same as the incandescent and the R9 was the highest of the LEDs I evaluated. At least these Waveform LEDs don't give me migraines though.
"Vibes" are fair. I just put flashlights with two incandescent-like LEDs (Nichia 519A and Nichia B35A in 2700K) and I can see a slight difference in how they render colors even though the spectrophotometer says all the major metrics are within a couple points of each other.
Looking closely at the measurements, when the B35A has an advantage on individual CRI samples, it's usually a larger gap than when the 519A has an advantage. They're both in the 90s for R1-14, and it takes a keen eye to tell the difference.
I recently learned about Color Rendering Index, which sounds like pseudoscience but apparently it is not. Here's a handy table I used for buying lights; again domain sounds grifty but, it's a searchable table :shrug: [0].
CRI is absolutely real. It's an old and relatively simplistic metric with several potential successors. The chart you linked uses one: TM30, which is based on the average of 99 different colors instead of CRI's 8.
There are seven extended samples for CRI (R9-R15) not included in the average. LEDs often do particularly poorly on R9, a measure of saturated red rendering. LED sources with high R9 usually advertise it separately.
Tint, or blackbody deviation (Duv) is also important to the look of light and listed on the chart, but not for every model. These numbers are very small, but important: anything outside of +/s 0.006 is not white light according to ANSI. +0.006 looks very green, and -0.006 looks very pink. Interestingly, after acclimating for a few minutes, most people think very pink looks better and more natural than neutral white[0]. Most people do not like green tint.
How do the reds look to you?
I looked at the photometric reports from a couple Waveform models on their website and the R9 (saturated red rendering) was in the 90s for both with tint almost exactly on the blackbody line. The 2700K did have a bit worse R9 than the 4000K so I could imagine it doesn't look exactly like an incandescent.