STM8S003F3 Interfacing with WS2811, external crystal required ?

1. I need to interface STM8S003F3 with WS2811. I want to know if external crystal is required for it or not, as WS2811 has very tight timings. I prefer to generate timing through NOP's for delay using inline functions

2. As STM8S003F3, Accuracy of Internal oscillator = +-5% over all temperature ranges.

3. WS2811 specifies:
a) T0H = 0.5μs ±150ns
b) T1H = 1.2μs ±150ns
c) T0L = 2.0μs ±150ns
d) T1L = 1.3μs ±150ns
e) RES = Above 50μs

4. With 16Mhz crystal, time for NOP is...

STM8S003F3 Interfacing with WS2811, external crystal required ?