Not really. You just need to know how to "wash" metal with a banana tip. (tube or pipe) Also called gouging. As you can see it would be quite visible from a distance if used...day or night.
It's done in shipyards quite frequently as, over time, outboard pipes get filled with barnacles.
Concrete and barnacles 'pop' as the interior pops back against the heat being applied to it.
(that guy was not washing the pipe away. listen for the 'pop' as the concrete overheated)
Washing the metal doesn't give the material inside time to heat up a lot and reduces popping.
A reciprocating saw would be less visible, but much slower, and would require quite a few blades if they are cheap ones (low quality metal used in fabrication) and present a problem on the back side unless the concrete was chipped away first.
Time is the opponent to the intended trespasser, not the material.
Banana tip? I probably know them as scarfing tips. We would never start an Owens-Corning glass melter demo without the iron workers having at least six on hand. Always Victor brand. Demo was such a nasty business.