It's not the same thing , for the nature_reserve ( a natura 2000 zone) the name is Plateau Engeland - Engelandplateau as signed on ground and also confirmed here : https://gardens.brussels/nl/groene-ruimten/engelandplateau or https://www.rtbf.be/article/uccle-la-zone-natura-2000-du-paisible-plateau-engeland-etendue-de-13-hectares-10142974

And we have the neighbourhood "Engeland" : 1247 : le lieu dit « Engeland »  (enge = prairie, herbage) est cité dans les écrits de l’époque.  C’est un site boisé, en continuité avec la forêt de Soignes

The neighbourhood also include "Les Promenades d'Uccle" (former wood) , Rue Engeland ... There is no official delimitation but there is a 'Plan Particulier d'’Affectation du Sol" that confirm at least that is 2 differents thinks https://www.uccle.be/sites/default/files/filemanager/Plan/PPAS-BBP/PPAS_BBP_10Bis_Quartier-engeland-Wijk-Engeland_2023_PLAN_U1180_fr_nl.pdf

