I think yours is yucca treculeana
https://davesgarden.com/guides... (bear in mind, there may be a odd schotti/fillifera mixed in there, shown in the link ) . At that size 40cm is too short. My yucca has leaves about 50cm (2,5 feet) . They peak at bout 65-70(3, 3/1 feet).
Gloriossa doesnt have serrated margins, they are often hard and woody. Also, not blue green, but dark green-blue(think young parodia magnfica) . very grainy. A bit of glaucous as well.
And that last part is very consistent btw. Ive not seen a non -glaucous gloriosa.
