Hi,
It's not correct, because there is no question about how you name it CIELAB, LAB, RGB, CMYK etc, but problem is how it works on illustrator - if i open fail in new based illustrator (24.0.1) everything seams to fine, but after copy and paste it in new blank document the visual and real color are canged, don't you get it ? ... please follow down here Vadim comment and you see it can't be so, color must stay same how ever you want to name it LAB, GRAB, WAD :) thats all, at least the program must be worn me about color changes

... dear friend belive, all designers over the world understud that, it's not nuclear physics, we only want help Adobe to improve and continue working with illustrator same level after updating, is it so hard to understund ?

best regards Ahti

HI
Pantone has never defined the colors in CMYK. This looks like as a comfortable solution but causing a lot of misunderstoods and incompatibilty. The orginal Pantone color defintion is in CIELAB, more precisely measured and stored as spectral values. CIELAB is used as a interpretation for using in applications not able to deal with spectral values. Next downstep is that the CMYK separation numbers are based on the profile of the intended output. As you maybe know best match of the spot color in a CMYK system is device dependent. Same CMYK could be very different on different printing systems. So CMYK is not "standard" for all output. To find the best CMYK replacement is calculated by CMS system depend on your color settings' working colorspace CMYK. There are many issue at the printers when they are printing from a file that contains those old school CMYK alternative data.
Pantone colors is intended for spotcolor printing not for CMYK. It is a long story why do they enabled that quirky CMYK replacement solution. If you want a nice blue in cmyk you should mixing that on color panel not refer to ReflexBlue. In this case, too, the output is important
If you have a brand color definition in spot color and if you want to print in CMYK rendering the best matching color, you should use conversion based on actual printing profile. Maybe the best workflow is that when you keep it as SpotColor with LAB values and leave the conversion task for an adequate colorserver or RIP. Keep in mind the X-Rite has redefined the complete PMS in 2010 on new medias ( OBA used in papers Coated and Uncoated,). Named as Pantone Plus C and U color library. The Pantone Plus contain more or less different shades under same name. In last 10 years they have extended with several hundred new colors also. Those old numbers in CMYK were used to help the operators with lean color knowlidge and applications' defficency and some marketing to use Pantone as a color standard. It is the same story with Pantone ColorBridge fan deck. It can use for some information only, but based on printing GraCol G7 system only. It is not a reference, not intended use for quality control or visual matching of production.
Adobe has changed the Pantone digital colorlibraries refering to changes. It is correct. All of the designer should understand these tools and handling.

This is mind-boggling. C'mon Adobe, we pay you a fortune. Files from last month now look like sh*it now that I upgraded???

Also If I open some file with pre-saved old Pantone Color (with CMYK-definition), the new CC2020 show it as Spot color with CMYK-definition mode.
But if I copy-paste object with this color to another file (new 2020 of old CC-generated file), the color change to "Book" with Lab-definition without any warnings.

Book.png

Thi is a big problem. Because You can made many changes in file and all stay correct, but one Copy-Paste change the color.