Some interesting things from Funakoshi, in his book Karate-Do Kyohan.
http://www.jka-slovenija.si/varovana/Prirocniki/Karate - do kyohan-1.pdf
Notice on page 23, where he talks about Uchi-te. Notice that this is the last of 7 types of blocking that he talks about. The other types are scooping, trapping, pulling, clearing... Then we get to Uchi-te or Striking Block (the classical blocks).
Striking Block (Uchi-te). The striking block is used in both attack and defense.
Attack vital points with the sword hand (shuto) or single-knuckle (ippon-ken)
fist; or, alternatively, strike with the sword hand (shuto) or wrist to knock an
attacking fist or foot out of the way. Once struck by a well-trained person who
is able to crack an opponent's bones, an attacker loses much of his desire to
fight.
Notice how Funakoshi says that these blocks are attacks to vital points, or alternatively can be used to knock an attacking fist or foot out of the way. (at the end of the book, a chart is shown of the vital points for these Uchi-te attacks.) Funakoshi says that the
classical blocks are the alternate versions of these techniques.
Notice step 8 in Heian Shodan:
8. FolIowing a block by the left hand of the opponent's right fist attack, the
point here is to grasp the opponent's right wrist with the left hand and, twisting
the grasped wrist in an outward direction, to break the opponent's right elbow
by bringing the right forearm up against it.
This is the "upper block" being used as a joint lock/break. This same concept shows up again and again in the kata, with Funakoshi referring back to this arm break description.
In Bassai step 12 he says:
Always remember that when the hand is pulled back to the hip after blocking,
as in this case, one must have the feeling of grasping the opponent and
pulling him in.
He is saying that in these katas, every block that then returns to chamber should be pulling something with it. This is not Uchi-te then, but one of the other pulling blocks (Hiki-te) he mentioned before the "classical blocks."
Now, go forward and look at the throws section. Notice how they start looking very similar to the "classical blocks" except that they are done as scooping, pulling or trapping blocks, off balancing and moving into the throws.
Throwing techniques include byobndaoshi, komanage, kubiuxi, kauuoaquruma., teubameqaeehi, yaridama, taniotoshi, udeuia, sakaieuchi, and others." All these techniques should be studied, referring to basic kata.
Essentially, these throws and others should be studied in the basic kata.
Yet somehow these days, we skip the first 6 blocking methods, and ignore the primary purpose of the 7th blocking method, to study the "classic blocks." What Funakoshi considered the alternate version, of his 7th way to receive an attack has now become the "classic blocks" studied in Karate. And when it is suggested to some that these should instead be strikes to the opponent... that is shrugged off as being some variation, when that was Funakoshi's primary application of those "blocks." However, he lists 6 other methods of receiving attacks, before the striking blocks. Reading through his description of the kata, most of the blocks come from the first 6 methods. Surprisingly, using those versions in the kata, allows you to move right into the throws he lists and more.