I think I know where you are going with this
Yes, it is somewhat subjective... I consider each player to have a region that is their personal space in which they handle their chips -- if they move their chips forward outside of that region, then it can be considered a forward motion, and he may be committed to putting them all into pot if the house rule is not "chip release" and if the betting action is not 100% clear. Often it is a motion that is the length of the forearm, or across where a "betting line" might otherwise be, but it could be less or more depending on the circumstances.
When there is
no betting line, I can see the action that Jack describes as being legal... just because you move forward with a whole handful of chips does not automatically mean that all of the chips are committed; if you do not hesitate, quickly cut out a certain number of chips and then bring the rest back to your stack, I have no problem with that as your action is clear. It's when you move chips forward and then hesitate with those chips in hand, that your bet is not 100% clear, and now you are at the mercy of the TD. With respect, I cannot agree with what Jack is saying in that part of the video because it appears that he is actually using an official betting line -- wouldn't the chips moved across the line be committed in a NL game? Isn't that the point of the betting line? I agree with you that this just complicates matters.
I can definitely see the merit of a betting line because you are turning the otherwise subjective assessment into something objective - you are either over the line with chips or not. One of the arguments often raised against the use of betting lines is that players who are unaware of the consequences of moving a whole stack across a betting line may get disproportionately penalized, or that there are strange circumstances that similarly would make committing chips to the pot seem unfair (e.g. if an "all-in" chip is used in conjunction with a line -
which I really don't like - and accidentally rolls over the line, chips from stacks falling forward over the line, etc.) -- but to me, the TD could always be given the discretion to be lenient in these types of situations, especially for first offences, so there may be ways to ensure that the application of the betting line is not overly strict.
My primary concern is a bit of a practical one - we can't really force every tournament poker table in the world to have a line, and also ensure that the betting line is a prescribed distance from the edge of the table. I'm not a fan of having some tables with lines while others in the same venue do not. I think at the end of the day, we may need to simply accept the fact that there will be a signficant number of tables without lines, and so we have to consider rules that can be applied at those tables. Ideally, either all tables had lines, or all tables would not have lines. But if we can't realistically have either, then IMO I think the "lowest common denominator" is a table without lines, and so the rules should at least be clear with respect to play at those tables.