It is a particular case of gijinka and mecha, where women in manga/anime style are representation or personifications of weapons or military equipment.
Female aircraft carrier. What clues or guarantees are there about her size? Will she be giantess
or normal size
Woman military boat. Note that on the right side there is a tiny
Another style of woman boat.
They can even be military science fiction equipment. In this case, it takes the Star of Death (Star Wars).
Particular case: MS Shojo
It is when a gundam (giant robot, mecha) acquires a human feminine personification. This personification must be so that the armor is the "clothing" (or armor) of the woman.
In its respective article explains why they are pseudo-giantesses and why it is popular within the GTS community: