There is a Shach in YD Siman 117 Sif-Katan 13 that brings there the idea of דאין במתנה משום גניבת דעת
What is the makor to this? What is the savara that there is no genevas hadas by a matana. Is this even true by a Yisrael (i.e. let’s say I give my friend a sefer that is in fact missing a number of pages and he think it’s the entire sefer.)
Answer:
The logic behind the ruling is that because it is a gift in any case, and the receiver will be in some way or other indebted to the giver, and we do not distinguish between different levels of gratitude.
However, the great majority of authorities do not concur with this ruling, in particular with regard to a Jew.
Please see here, no. 1 and note 4, and here, no. 3-4 and note 11.
