I wonder if I should ask Sporty's or King Schools for the template they
use for their endorsements. All their ads (and websites) claim their
courses are for "Private Pilot" - no "airplane" qualifier obvious to me,
anyway. No doubt they believe that goes without saying in their airplane-
centric world.


No, Hartley and Chip gave you the correct advice.

6. Aeronautical Knowledge - FAR 61.35(a) & 61.105(b)(1-13)
I certify that I have given Mr/Ms the applicable ground instruction
required by FAR 61.105(b)(1-13) and find him/her prepared for the
private pilot - glider aeronautical knowledge test.

FAR 61.105 reads:
§ 61.105 Aeronautical knowledge.

(a) General. A person who is applying for a private pilot certificate
must receive and log ground training from an authorized instructor or
complete a home-study course on the aeronautical knowledge areas of
paragraph (b) of this section that apply to the aircraft category and
class rating sought.

Note that the test is for category and class. The category in this case
is "glider" (category examples a airplane, glider, helicopter, etc).

Tony V. CFIG