Not weird at all and is an advanced technique commonly used by SCOW and sportboat racers and others who race relatively flat bottomed or tunnel hulled centerboard boats.
Notice that the leech of the mainsail is 'well closed' by pulling LOTS of strain on the mainsheet. This causes the leech (especially on boats with large 'roach areas') to become quite rounded up towards the weather side and which causes the 'overall amount' of draft to radically increase, .... causes the boat to radically heel over and in doing so causes a vast reduction of hull wetted surface area
. With less hull drag, the boat speed increases and the ability to point may increase by 10-15 degrees (because of the radical change in 'angle of attack' in the mainsail due to that 'closed up' leech shape) .... momentarily for many seconds.
In light winds on the big ILYA Scows etc., you can earlier begin to 'plane to windward'; on a keel boat you can commence to 'turbo sail' (constantly and slowly varying between a 'high' beat and a 'foot off') & which will ultimately leave your straight line sailing competitor well to leeward ... your keel better 'flys (lifts) to windward' when at the induced artificial 'higher' apparent wind (both angle and velocity).
Ditto too when racing and you near the end of a leg before a tack ... and forcibly pointing higher (power pinching) is inconsequential to VMG; but, you gain considerable 'boat lengths' on the 'next' leg because youre 'power pinching' up. I used to do this routinely on the last 5% of every beating leg ... even on a keelboat. Sailboat racing is a game of 'inches gained' and such will gobble up MANY inches when done correctly; but it takes a LOT of practice to get it right.
This 'technique' is derived from the aero theory of airflow 'recirculating around
a sail(s)', and by doing so transiently causes the (vector component of) FORWARD
FLOW of air on the windward side of a sail to cause MORE 'upwash' in front of the boat/jib .... something akin to roll-tacking but without any turning.
"Turbo sailing": Footing Off - SailboatOwners.com
... see POST #12