The Chironja Grapefuit is as far I know not a real Grepfruit. It is presumably < hybrid between Grapefruit and Orange, therefore also called Orangelo
It is said that in the year 1956 Carlos G. Moscoso of the Department of Horticulture of the University of Puerto Rico found a wild seedling tree in the rural mountainous Angeles and Caguanas areas of Utuado municipality, which produced large, bright yellow fruit, and other seedling trees were found in isolated areas among the coffee plantations. The name Chironja is a combination of Chi(na), the local term used for the sweet orange, and (to)ronja, the Spanish word for grapefruit.
In
https://citrusvariety.ucr.edu/citrus/chironja_3909.html it is also listed as a Grapefruit hybrid - with the marking CRC 3909.
According to knowledge that it is presumably a hybrif Grapefruit whicht is not hardy and also sweet orange which is also not hardy I agree with you to put it during the winter into inside or into a greenhouse in any case is the safe method - if you can get this citrus variety in your country
