When the word ‘drawing’ is pronounced as /’drɔːrɪŋ/, is that R called intrusive? Is such pronunciation colloquial and unacceptable for formal address?
For people who use the term “intrusive r”, it refers to linking /r/ whenever it occurs in a context where the letter R isn’t written. It doesn’t make a difference whether it is between words (as in saw it) or within a word (as in drawing).
Asking whether “intrusive r” is “colloquial and unacceptable for formal address” is a separate question. Pronouncing “intrusive r”s was traditionally viewed as incorrect but its frequency in current non-rhotic Southern British English accents is high enough that it doesn’t make too much sense to call it “unacceptable” if you’re trying to describe actual usage.