This is incorrect. Rather chicken can be Haraam if it is not slaughtered correctly.
حُرِّمَتْ عَلَيْكُمُ الْمَيْتَةُ وَالدَّمُ وَلَحْمُ الْخِنْزِيرِ وَمَا أُهِلَّ لِغَيْرِ اللَّهِ بِهِ وَالْمُنْخَنِقَةُ وَالْمَوْقُوذَةُ وَالْمُتَرَدِّيَةُ وَالنَّطِيحَةُ وَمَا أَكَلَ السَّبُعُ إِلَّا مَا ذَكَّيْتُمْ وَمَا ذُبِحَ عَلَى النُّصُبِ
Forbidden to you is carrion, blood, the flesh of swine, that over which any name other than Allah’s has been invoked, an animal that has been strangled, beaten to death, killed by a fall, gored to death, or (partially) eaten by a beast of prey, except that which you manage to slaughter (while it was still alive), and [forbidden to you is] all that has been slaughtered on altars. (Surah al-Maidah, 3)
The Holy verse above makes it clear that animals that are not killed by correct and valid slaughter are prohibited (Haraam) to consume. The person who made the above statement may have been referring to the fact that chicken will remain Halal even if the entire head is cut off. Such an act is Makruh but will not render the meat Haraam.
قَطَعَ الرَّأْسَ كُرِهَ لَهُ ذَلِكَ وَتُؤْكَلُ ذَبِيحَتُهُ (الهداية)
(If) he cuts of the head (of this animal) then his action is Makruh, however the slaughtered animal remains Halal to eat. (Imam al-Marghenani, al-Hidayah).
If this is what the person was referring to, then it is correct. However, his actual statement was completely incorrect and contradicts the Quran and Sunnah. People must be incredibly careful when speaking about the Deen of Allah (Most High), mistakes can lead to misguidance and one will be responsible for it.
And Allah (Most High) knows best.
– Answered by Shaykh Noorud-deen (08.02.2021)
Is stunning before slaughter allowed?