The wikipedia's Voiceless alveolar sibilants section states:
The voiceless alveolar sibilant is a common consonant sound in vocal languages. It is the sound in English words such as sea and pass, and is represented in the International Phonetic Alphabet with ⟨s⟩. It has a characteristic high-pitched, highly perceptible hissing sound. For this reason, it is often used to get someone's attention, using a call often written as sssst! or psssst!.
However is the English sibilant 's' truly alveolar for everyone or does it have some dental/post-dental quality to it for some native speakers? What I mean is whether the tongue tip is not supposed to touch the back of the upper teeth
As Alveolar consonant states:
Alveolar consonants (/ælˈviːələr, ˌælviˈoʊlər/) are articulated with the tongue against or close to the superior alveolar ridge, which is called that because it contains the alveoli (the sockets) of the superior teeth. Alveolar consonants may be articulated with the tip of the tongue (the apical consonants), as in English, or with the flat of the tongue just above the tip (the "blade" of the tongue; called laminal consonants), as in French and Spanish. The laminal alveolar articulation is often mistakenly called dental, because the tip of the tongue can be seen near to or touching the teeth. However, it is the rearmost point of contact that defines the place of articulation;
So as per the above, could the tip of the tongue be touching the back of the upper teeth for the English 's'? That is, does its characterization as an alevolar sibilant prohibit the tip of the tongue from touching the back of the upper teeth during its articulation?