It is possible that there was a mistake on a video - I will look into it. The fittings on the flow sensors are most certainly BSPP.
Looking at the photos of the different flow meters on your website, it appears to me that the 2" size could be BSPP, but the 1" and 1/2" sizes are BSPT. The 1/2" size is definitely BSPT. So I think everyone is a little bit right!
BSPP are not a tapered thread and seal by compressing a sealing washer between a shoulder on the male side and the face of the female side. The photo of the 2" meter shows what appears could be a shoulder; the 1" is questionable, but that 1/2" meter definitely has no shoulder.
For low pressure applications, the taper found on "xPT" fittings is not critical to make the seal.
The important part (in most all of our aquarium applications) is that the thread pitch and angle is correct - that is the key difference between "NPx" and "BSPx" fittings.
NPx = NPT (there's only one option): tapered thread, seals by interference at the threads.
BSPT: tapered thread, seals by interference at the threads. Similar to NPT, but has a different thread pitch than NPT... but only by a fraction of an inch.
BSPP: parallel thread, seals by a sealing washer between the faces of the male and female fittings. Can also be referred to as a "G" thread.
As a end user, it's really easy to mismatch NPT and BSPT because they're both interference fit threads. Even with properly matched NPT fittings, you screw them together a few turns and then they start to bind up... like they're supposed to in order to form a seal. But if you screw in a NPT to a BSPT, it starts to thread just like a normal NPT fitting but binds up just a little bit sooner. That binding isn't due to the designed interference of the threaded joint like a normal NPT, but the mismatch in thread pitch. You think you've got a good joint, but when you put pressure to it, it leaks.