Anybody who calls upon saints from afar believes by NECASSITY that his buried saints can hear, see etc everything. This person has knowingly or unknowingly deitified his saints.
This is why Mushrikūn call on their buried gods in the first place; they already hold shirki beliefs that they and their Rabbis and priests justify with mental gymnastics, fallicious analogies and other pathetic excuses (such as: “My saint can hear and respond to unlimited calls, but not as many as Allah”…’Allah can create millions of Jesus’ and Ali’s who can aid us…why not? with the persmission of Allah…blah blah…’).
These are simple Lawāzim that come with such practices, and this is why scholars such as Ibn Uthaymin, Nasir al-Barrak etc rightfully excused ONLY those who ask the Prophet (s) right next to his grave to ASK Allah (only for Shafa’ah). This is undoubtly not Shirk as the one doing it has some form of (although incorrect) Shubuhat (Prophets alive in heir graves etc.) AND, most importantly, the doer doesn’t believe that the Prophet can is aware of every call, can hear every call, can respond to every call etc. i.e. he hasn’t deitified the Prophet (s) in any shape whatsoever.
PS: Quburiyun denying their Ibada by calling it ‘Tawassul’/’Wasilah’/’Shafa’ah’ or adding their favourite clause of ‘Bi`idhnillah’ to their shirk doesn’t turn their paganism into Tawhid. Matters are judged based on their reality and not what they are called.