I know if you call HC they will tell you that the only source is from an LP. However if you read the legislation, the legislation says that we "may" purchase from an LP, not that we "must".
In talking to HC people (at least the ones answering the phones) they have said a number of things were a certain way, but reading the legislation it is rather open ended.
I know what you're saying, I've seen that too on their brief version/web site and forms it seems open ended.
You prompted me to find the full document which was last updated Dec. 6th and while it's not clear there either. I did find some interesting stuff in there related to seeds. Mainly some items pertaining to storage and carry counts, worth a read as it could cause some issues for registered folks.
Here's an extract of anything pertaining to seeds, each is marked with the section/item in the full document.
Demonstrate authority to possess or produce
15
An individual who, in accordance with these Regulations,
possesses or produces fresh or dried marihuana,
cannabis oil or marihuana plants or seeds or a product
referred to in paragraph 4(1)(b) or (c)
must, on demand,
demonstrate to a police officer that the possession or
production is authorized.
Prohibition — obtaining from more than one source
16 (1) It is prohibited to seek or obtain fresh or dried
marihuana, cannabis oil or marihuana plants or
seeds
from more than one source at a time on the basis of the
same medical document.
Equivalency factor
(2) For the purposes of paragraph (1)(f),
three marihuana
seeds are equivalent to one marihuana plant
Section 187:
(c) transport directly, from the site for the storage of
cannabis to the site for the production of marihuana
plants, a
total quantity of marihuana plants and seeds
that,
taking into account the equivalency factor specified
in subsection 145(2),
does not exceed the equivalent
of the maximum number of plants, determined in
accordance with section 190, that are authorized to be
under production under the registration;