Yes. This is something that is difficult to understand for people those who are new to Buddha Dhamma. While there are many myths associated with Buddha Dhamma (i.e., ability to bring in rain with prayers, etc), there are some phenomena like this that are genuine.
When one becomes an Arahant, there are some drastic changes that happens in one’s physical body, in addition to those in the mind. For example, one’s bones get crystallized and can survive thousands of years. These are called “dhatu”. Buddha’s dhatu survive (in open caskets), and are being worshipped even today. They are supposed to survive until the end of Gotama Buddha’s Buddha Sasana (Ministry), which is supposed to last 2500 years more.
The reason that an Arahant‘s body cannot stay alive as a “householder” is similar to the reason that an Arahant will not be reborn even if more kammic energy for the human bhava is left. The mindset of an Arahant cannot be “born” with the body of a gandhabba. Why an Arahant needs to become a bhikkhu(ni) is a bit more complex. But becoming a bhikkhu(ni) makes a difference.
However, becoming an Arahant will not happen accidentally, so one does not need to worry. One WILL know if that happens. It is very difficult to attain.
Long before that one would become an Anagami, and that is not easy either. It should be relatively easy to verify whether one has become an Anagami. One would have lost all sensual cravings (for food, music, scents, any person or anything including one’s possessions like money, houses, properties, and sex). So, there will be many drastic changes in one’s mindset as well as in one’s body well before one gets to the Arahant stage.