The AIM says exactly what I said because I quoted it.
No, you said this:
It explicitly says “ if no hold has been assigned and there is frequency congestion”.
The AIM actually says this, which isn't the same:
5−3−8. Holding
a. Whenever an aircraft is cleared to a fix other
than the destination airport and delay is expected, it
is the responsibility of ATC to issue complete holding
instructions (unless the pattern is charted), an EFC
time and best estimate of any additional en route/terminal delay.
NOTE−
Only those holding patterns depicted on U.S. government
or commercially produced (meeting FAA requirements)
low/high altitude en route, and area or STAR charts should
be used.
b. If the holding pattern is charted and the
controller doesn’t issue complete holding instruc-
tions, the pilot is expected to hold as depicted on the
appropriate chart. When the pattern is charted on the
assigned procedure or route being flown, ATC may
omit all holding instructions except the charted holding
direction and the statement AS PUBLISHED;
for example, HOLD EAST AS PUBLISHED.
ATC must always issue complete holding instructions
when pilots request them.
c. If no holding pattern is charted and holding
instructions have not been issued, the pilot should ask
ATC for holding instructions prior to reaching the fix.
This procedure will eliminate the possibility of an
aircraft entering a holding pattern other than that
desired by ATC. If unable to obtain holding
instructions prior to reaching the fix (due to
frequency congestion, stuck microphone, etc.), then
enter a standard pattern on the course on which the
aircraft approached the fix and request further
clearance as soon as possible. In this event, the
altitude/flight level of the aircraft at the clearance
limit will be protected so that separation will be
provided as required.
d. When an aircraft is 3 minutes or less from a
clearance limit and a clearance beyond the fix has not
been received, the pilot is expected to start a speed
reduction so that the aircraft will cross the fix,
initially, at or below the maximum holding airspeed.
e. When no delay is expected, the controller
should issue a clearance beyond the fix as soon as
possible and, whenever possible, at least 5 minutes
before the aircraft reaches the clearance limit.
f. Pilots should report to ATC the time and
altitude/flight level at which the aircraft reaches the
clearance limit and report leaving the clearance limit.
NOTE−
In the event of two-way communications failure, pilots are
required to comply with 14 CFR Section 91.185.
First, ATC has to give you a clearance limit before this paragraph even applies. Once you know, by whatever verbiage they convey their intent to hold you, this section kicks in as to "how" to hold, i.e., your "holding instructions". It does not mean "if no hold has been assigned", it means "if no 'holding instructions' have been assigned", that is, which direction from the fix, etc.
The AIM says that if you don't have instructions to hold, but you reach the last point you have been authorized to fly to and cannot get further authorization because of a temporary measure, such as frequency congestion, then you enter a pattern to hold at that point along your last heading.
This is somewhat correct. You hold on the arrival course at the fix, not the "heading". Also, if you "don't have instructions to hold", you won't have a "last point you have been authorized to fly to" as per above. A "clearance limit" means "holding fix".
Hope you enjoyed McDonalds.
There was a long line of cars stacked up in a holding pattern, so I went to my alternate: Burger King.
