According to a quote attributed to the UN Food and Agriculture Organisation, the 'meat trimmings' used in hot dogs encompass a little more than what we might think of as some meat trimmed off the bone....
http://https://www.businessinsider.com/what-are-hot-dogs-really-made-of-2014-7?r=AU&IR=T
From the webpage above, quoting the UN FAO,
"The raw meat materials used for precooked-cooked products are lower-grade muscle trimmings, fatty tissues, head meat, animal feet, animal skin, blood, liver and other edible slaughter by-products."
In other words pretty much as stated in Col's graphic.
Although like anything, who's to say what does or doesn't take place in every meat processing plant? A video might be instructive on the above.
Best
JA