ELS with P for probability

These are samples from a worksheet on Probability:

P(A and 1)
P(a vowel and a number)
P(heads and a 1 or 3)

These are all stand-alone phrases, not parts of equations.
From numerous NBA workshop materials, I have deduced that the P for probability does not require the ELS in any of these examples.
I think, from the explanation below, I understand why , but it seems anything but intuitive and so it would help to know what rule from the Nemeth Code would lead me to the same deduction -- the next time I encounter probability!
Are there instances when the P followed by parentheses would require an ELS?

From NBA Professional Development Conference materials (Fall 2008) High School p61:
partial example: P(A and B)
comment: "P(A" are not single letters. If the opening grouping symbol and the space it occupies were removed, "P" and "A" would be adjacent and neither would require the ELI.

From NBA Abbreviations workshop materials (Spring 1999) p8:
example: P(four or more breakdowns per day) = .1
comments: "P(four" -- if the opening grouping symbol and the space it occupies were removed, the letter would be followed by a word and not qualify as a single letter. All contractions are used within the grouping symbols as none are in contact with any symbols which forbid their use.