Not only is this (somewhat obviously given the discovered bias) wrong, it’s physically impossible to bias a coin flip by weighting one side. Weighting a coin will change its center of gravity but to bias a flip you would need to impart angular momentum while it is in the air; at any constant rate of spin (again somewhat obviously once pointed out) each side will spend 50% of its time "up" and 50% "down".
There's a huge assumption in this assertion: that you catch the coin.
If you let it bounce on a table, it's much more likely to land heavy-side down. Just imagine a very thick coin one side lead the other side balsa wood. That would land lead-side down much more than 50/50 if allowed to bounce on the table.
If you flip toast rather than drop it, it doesn’t. Also, if you drop it it doesn’t really land “butter side down” but “top side down”. Just butter the bottom of your toast to solve the problem!
https://www.tandfonline.com/doi/abs/10.1198/000313002605