Yes and no, lol

I never heard of it called a hashtag until the early days of instant messaging/social media other than in various programming languages. Beyond that, it has always (at least in the US) been called a pound sign such as a 5 # bag, etc. Also, as Richard says in his videos it's been called the Octothorpe from "Octo" referring to the 8-points.

It's also known in rural Ohio as a "Tic-Tac-Toe" board, lol.

Britannica, also, says that the symbol originated as the Roman pound (lb)  for libra pondo (pound in weight) that kind of looks like 2 curive lowercase "L"'s with lines through them

It can be confusing.  I had a similar experience at an English market when I saw meat priced in pound/pound.  Also, in the US, a boot and a bonnet are things you wear, not parts of an automobile.  (Jeremy Clarkson had fun with this in Top Gear/Grand Tour.)

Some of the language differences are entertaining.  In the southern US, biscuits and gravy is a popular breakfast dish.  From the UK perspective, this may seem revolting but the biscuits and the gravy are not what you may expect.  For me, that is part of the fun of meeting people from different places.

Fries are chips. Chips are crisps. Learned that in my recent visit to the UK. Lol