There is a quite recent article which may be of interest to some.
This article details how some Tibetan Buddhist monks apparently may enter thukdam at the time of physical death and for some time, usually a few days, their body does not seem to decompose.
The related medical research so far (January 2021) is described in the following article:
There are a couple of interesting points, at least.
This thukdam experience reminds in part the description of jhana.
As far as I know, the only medical test on jhana so far is reported in this paper:
It is interesting that the Dalai Lama has involved some of the monks in this project and in related scientific research.
Whatever is going on inside thukdam meditators, His Holiness would dearly like to know. Heâs been asking scientists to study the mysterious state for nearly 20 years, with little apparent successâuntil recently, when his friend Davidson and other researchers at University of Wisconsin-Madisonâs Center for Healthy Minds created âThe Thukdam Project.â
Interesting. I was just reading a passage from the Abhidharmakosha which cites a sutra that speaks of the Buddhaâs ability to expend his life (ayus) and life force. Of course we know the Mahaparanibbana sutta mentions this ability, though it doesnât explain it as something that happens after the âdeathâ of the body. Perhaps this is somewhat related to this kind of ability.
Maybe indeed, thanks for the references.
Since it is mentioned that in thukdam the body is still warm and that reportedly there is a vision of light (changing from whitish, to reddish to black), I would tend to think that this may be a jhana state reached just before the physical death, preceded by a nimitta. In this case, someone who has mastered the jhanas may be able to get it at the right time. This may also explain your quote.