What's the idea behind the no-feeding-in-the-last-20-km rule? I'm trying to understand the reasoning behind the no-feeding in the last 20 km rule. In the Tour de France 2020 Julian Alaphilippe lost his lead due to an infraction of this rule.
Might it be:

The competitors are in full sprint. It's too risky to be distracted by using one hand for food/drink.
It's unhealthy for the competitors, since for the food to be beneficial, it'll have to be pure glucose. There is too little time left to digest anything more complex, and if they don't get it exactly right, they could &quot;hit the wall&quot;.
Food in the last stretch starts to act as a deciding factor. A team that discovers a concoction that provides an unfair advantage would win based purely on that food/drink, not the ability of the racers.

I'm sure the reasoning is well established. Is it also well known? More personally, does the rule matter for the amateur? Is there any reason why an amateur should not eat/drink in the last ~20% (if not 20 km) of a trip?
Update:

(The following thought emerges from Vladimir's and Weiwen's answers.) Might I have been sloppily confusing the verbs &quot;feeding&quot; and &quot;feeding oneself&quot;, and might the rule be more easily expressible in the precision of French's distinction between reflexive and non-reflexive verbs? In other words, it is perfectly allowed to feed oneself (&quot;se nourir&quot;) during the last 20 km. What's not allowed is to give (or take) food from someone else (&quot;nourir&quot;). The rule would be clearer if we start to split hairs and ask whether it's allowed for a helper (&quot;domestique&quot;) to pass some food to a hungry (and more important) team leader during the last 20 km.

Gratuitous and unrelated comment/question, now that I'm noticing that all the cars clear out during the last 20 km: How do the cyclists tolerate inhaling the exhaust of so many cars during the race until the 20-km mark? It's one thing for a (gasoline) car to pass by; it's another to remain behind it—inhaling the discernibly worse air—for hours on end.
If you do not race in a UCI  race you do not care about this rule at all. If you are thirsty, you drink. The end of the trip is where you are at the greatest danger of bonking so if you feel hungry or weak, just eat or get some quick sugar.
Actually, the racers can also do so, but they cannot get new food and new water, they only can use what they have.
UCI Rule 18:
&quot;All feeding (from a car and on foot outside of the feeding zones signposted by the organiser) is strictly forbidden: during the 30 first and last 20 kilometres; ...&quot;
If you are just eating your own food or drinking your own water, you are not acting against any imaginary rule on your trips.
I do not think any of the reasons you list is exactly the right one. The closest one would be number 1, but not literally. They are not in full sprint, but disruptions and distractions have to be prevented at some point. And by default that point is 20 km. Sometimes it is postponed when the weather is hot.

Reaction to the update:
I do not think that passing a bottle from a domestique to the leader is forbidden, but I am not sure. It does not appear to be against the wording. I really do think the rule is to prevent the distractions from team cars and from riders moving to the side of the road in the deciding parts of the race. The wording appears to be clearly against external feeding and not against feeding yourself at all.