Personally, I have never seen any referee, at any level of the game, penalise a downfield player for offside (under the 10M law or otherwise) when the ball has been clearly touched in flight. On the contrary, most referees will yell "touched" so all players know that everyone downfield is onside. Pulling out the whistle and PKing a player for 10M offside after yelling "touched" would count as a real "gotcha" moment.
Its important to keep in mind that 10M law is all about where the ball lands or is caught after being kicked.
[LAWS]Law 10.4. An offside player may be penalised, if that player:
c: 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.
[/LAWS]
The ball touched in flight has not been caught, nor has it landed, so that makes all players onside irrespective of the 10M Law. That the ball will land later is irrelevant, because the last player who played the ball was an opponent, so all those players have been previously made onside under law 10.1. Law 10.4c cannot override that.
IMO This Law was written with the intention of not making any downfield team-mates of the kicker onside when an opponent near where the ball lands, touches or plays the ball in an unsuccessful attempt to field it, for example, an opponent attempts to catch the ball but drops it behind him. An action like that will put those players onside in scenarios where the 10M Law does not apply
[LAWS]Law 10.7: Other than under Law 10.4c, an offside player can be put onside when:
b: An opponent of that player.
i: Carries the ball five metres, or
ii.Passes the ball, or
iii: Kicks the ball, or
iv Intentionally touches the ball without gaining possession of it.[/LAWS]
As often happens in here, the Law has been over-analysed to the nth degree, in discussions involving numbers of angels on pin heads. This is unhelpful to newish referees looking for answers. The words printed in the Laws do not matter as much as how they are officially interpreted - what really matters is what advice we should give to referees should they encounter this scenario in their games. My advice would be that, when a player attempts to block a kick, and the ball is touched in flight by the blocker, then all players of both sides that are downfield of the blocker, are onside.