I believe the flight was at or below other flights that day.  They were at less than 250 feet.  The wide angle lens of the camera makes it seem like you are much higher than you actually are. 

I have seen videos taken years ago over a lake.  The view made it look like the shots were taken 600-700 feet high.  Then you find out from topographical maps that the surrounding hills are only 275 feet high.  Careful examination of those old videos clearly showed the hills are above the camera.

That echos the results of some tests using recording altimeters in Ontario, at a MAAC field.  I believe it was done in the summer of 2022. They found that people consistently over estimated the height of their planes.  Over many flights a very small number were over 400 feet AGL. 

Several years ago I observed someone flying a large glider at the MAST site in Truro.  They said words to the effect, that is what such and such feet looks like.  I said I thought it was closer to a much lower number.  It was way lower.  If I recall their estimate was off by up to 75%.

The reason I know was they had an altimeter sending telemetry to a display near their flight box.  They said take a look.  I did.  My estimate was withing 50 feet of the telemetry.  They were not observing it, just letting the flight record for later examination.  So that person's estimate was just that, an estimate, and wildly inaccurate.

If you know the focal length of the camera lens, there are ways to calculate distance and altitude.  Just watching the video can be very deceptive.

So I don't think the person that took the video of the field should have any concerns about altitude.  The person who shot the video has apparently been flying that same plane for over 20 years.

I have still photos taken while flying from Shannon Park field many years ago, as does John O.  It was hard to take sweeping panoramas.  I have a shot that was taken looking down at the MacKay bridge.  People might think it was taken 1000s of feet high.  Then you realize the top of the towers on the bridge are 320 feet above sea level.  So being above it probably meant that you were still below or slightly above 400 feet AGL. 

Other photos show being close to the altitude of the stacks at Tuft's Cove.  The plane was small in the air.  The stacks are not 400 feet tall. 

With lots of photos, and known landmarks, altitude can be fairly closely determined.  My estimation of altitude is based on figuring out altitude from dozens of pictures of landmarks and viewing 1000s of aerial photos. So I stand by my estimate that the video at the field was way below 400 feet.