firstly. what you are sending through routes is not BTC. its an invoice measured in millisats. a unit of measure the bitcoin network does not understand and in a packet of data the bitcoin network would not accept.
these invoices and htlc secret reveals are not bitcoin network compatible.they are their own format.
H2O can take the form of water, ice or steam. Steam can't flow in a river but it's still H2O.
BTC can take the form of satoshis or millisats. They're still BTC
While by no mean I want to start a flame war, I think that I've understood what he means.
His point is that LN acts like a hose. It doesn't care if it will transport water (bitcoin), oil (name your altcoin) or even air (if it's tight). It will work the same, depending on where it's plugged.
While LN can be seen as an extra layer for Bitcoin, it can be an extra layer for whatever. This is what I've understood.
BUT at the end of the day it doesn't matter what else the hose can transport as long as we can use it for our needs.
At the moment the hose is plugged to 2 holes of a water pipe, it's a water hose. So... why argue for tiny details?!