It's him expressing his opinion that it is not a "timer" as opposed to what he might call a proper timer such as an RTC or a crystal oscillator which have longer term stability.
It's semantics. If he wants to define a timer by it's internal ability to generate pulses and not by external components then that's fine. With resistors and capacitors a 555 can set off a buzzer after a predetermined amount of time and I think most people would consider that good enough to call it a timer.
Is there a difference between the two outside of the way they keep track of time?