The RB211 as you point out has the rubber tit! which by design would 'wobble', and shed any ice should it attempt to form as it gets out of balance.
JFI if that rubber tit is missing it's a 'No dispatch'.
Gents
It is a common misunderstanding, that a missing rubber tip is a NOGO.
AMM for RB221 TR700
Subtask 72-35-41-220-050- 0
A.
Examine the air intake fairing/spinner.
(1)
Examine the rubber tip.
(a)
If the rubber tip is not there, accept if:
1
The spinner is replaced before 5 flights
Rgds