My mum used to say to me and my brothers "what's your name Pa'erson with 2 tees" whenever we said bu'er or wa'er - I can assure you that the glottal stop is widely used in dialects on the English continuum in Scotland ;-)
That matters if a speaker of the former language tries to learn the latter. It's hard to learn to reliably make a phonetic distinction that has never mattered for comprehension before. See also Japanese speakers struggling to distinguish "rock" and "lock" in English.