A will/share-transfer scheme which minimises death

A (potentially: KEY) fact you do not here make (and, unless I do not
recall correctly, in your other postings have not made) sufficiently
clear is whether the transfer of ownership of the shares in question
from the then owner (the corporation itself? your father?) to the
transferees named in the corporate resolutions adopted to implement
the share-transfer/tax-avoidance/(later)loan-forgiveness scheme to
which your refer were reflected clearly on the corporation's
share-transfer books/records maintained in the ordinary course of
business.

A related insuffiently clear fact (though, maybe, I just don't
remember what you said in this respect) is whether the shares
themselves were actually tendered to and accepted by the transferrees
or, if not, whether there was a provably established corporate
practice for the corporation itself to act as custodian for such
shares.

It may be important to know more about what you "...snip..." because
might help answer the (as far as I recall from your postings on this
subject) unanswered questions summarized above and also because, in
any event, the present tense "you cannot absolve" is not suffiently
clear about what a _will_ -- when the will becomes effective -- may
absolve.
It is generally correct that a unilaterally stated agreement by an
individual or corporate body (at least if not supported by provable
present consideration [apparently not relevant here] or [as you
_otherwise_ correctly say] not supported by an agreement signed by the
party to be charged [you]) to absolve a future debt is not enforceable
(for lack of consideration or for lack of such a signed agreement).

HOWEVER, you seem to be referring to two different/independent
undertakings to absolve a debt -- first, a corporation's promise to do
so (as stated in and implemented by duly enacted corporate resolution)

and, second, an _individual's_ instruction to do so, as stated in his
will, i.e., in/by an instrument that will not take effect until the
date of his death.
In Gt. Britain and in the U.S., however (I haven't verified whether
there is a different rule on point in So. Africa), because a will
"speaks" (only) as of the date of the testator's/testatrix's death,
the dispositive question insofar as an absolution-of-debts provision
stated therein is concerned will be whether the subject of such
absolution was indebted to the deceased when the deceased died (again:
NOT whether the target of such absolution was indebted to the
eventually-to-be-deceased before or when s/he made the will in
question).
(This is a corrolary to the related will-related rule, applicable in
your country as in the Gt. Britain and in the U.S., that a will which
directs,
"I leave my house and the land on
which it is erected to [beneficaryX]"
will not be interpreted/applied to require that the will-maker will
not have been entitled to sell or give that property to another before
s/he died in the absence, in addition to the will, of an agreement
with [beneficiaryX] that s/he may not and shall not do this.)

It is a very safe bet that this is a misreading or, at least, that
your "extract[ion]" is (seriously) incomplete. The rule, insofar as
it is that, you "extract" applies to CONTRACTS by which someone AGREES
to make a donation, not to "donations" in general (if the donation
actually has been made).
Which is why clearer answers are needed to the questions when/how
the corporation in question and the (original) shareholder in question
handled transfers of corporate stock from the corporation to a
third-party or from that (original) shareholder to a third-person
(e.g., to you).