By utter coincidence, I was wondering around this over the weekend while doing some refresher reading of the laws...
In situations like this we hear the ref call "touched" or "touched in flight", with the implication that all players on the kicking team are now onside wherever they are positioned. HOWEVER...
Law 10.4.c
An offside player may be penalised, if that player:
Was in front of a team-mate who kicked the ball and fails to retire immediately behind an onside team-mate or an imaginary line across the field 10 metres on that player’s side from where the ball is caught or lands, even if it hits a goal post or crossbar first. If this involves more than one player, then the player closest to where the ball lands or is caught is the one penalised. This is known as the 10-metre law and
still applies if the ball touches or is played by an opponent but not when the kick is charged down.
Law 10.8
A player offside under Law 10.4c cannot be put onside by any action of an opponent, apart from a charge down.
Law 11.5
The ball is not knocked-on, and play continues, if:
A player knocks the ball forward immediately after an opponent has kicked it (
charge down).
Sadly the "charge down" is not included in the definitions section. Therefore, based on Law 11, we can define a charge down as being when "A player knocks the ball forward immediately after an opponent has kicked it".
(Well, let's come back to this in the last paragraph below...)
From law 10.4.c we know that a charge down is treated differently to when the "ball touches or is played by an opponent" with regard to offside lines after a ball is kicked.
In the linked video, the LEI player is within 10m of where the ball is caught or lands. The Bath player touches the ball but does not execute a charge down. The 10-metre law still applies if the ball touches or is played by an opponent, therefore the LEI player is offside.
Hypothetical, if the LEI player was in front of the kicker
but not within 10m of where the ball landed, then we should be looking at law 10.7. Although the LEI player would be offside at the moment of the kick, but...
Law 10.7.b.iv
Other than under Law 10.4c, an offside player can be put onside when:
An opponent of that player:
Intentionally touches the ball without gaining possession of it.
... immediately after the kick a Bath player intentionally touches the ball without gaining possession of it, thereby putting the LEI player onside (in my hypothetical that the LEI player is NOT within 10m of where the ball lands).
HOWEVER, despite the wording provided in Law 10, the video provided to illustrate Law 10.7.b.iv matches the incident in the OP video (totally ignoring law 10.4.c). Also, the video illustrating Law 10.8 shows an attempted charge down but the ball continues up the field (i.e. the defender does not knock the ball forward) and play continues with players from the kicker's team considered to be onside (again, apparently ignoring law 10.4.c).
Thus, the videos associated with laws 10.7 and 10.8 imply any attempt at a charge down resulting in contact with the ball is regarded as being a charge down, therefore law 10.4.c does not apply. However, I would like to know, with regard to law 10.4.c what is the difference between "ball touches or is played by an opponent" and a "charge down".... they must be different, otherwise law 10.4.c would not list them associated with different outcomes.