Homophones are sometimes more than a word. Sometimes phrasal homophones are called ‘oronyms’ In this example, the two phrases are phonetically identical, and this is made possible by the phenomenon of linking: in this instance, it is not possible to say with certainty whether a /t/ consonant is at the end of one word or at the beginning of the next!
Isn’t there a minute difference between the pronunciations of these two expressions? The /t/ in boat eyes seems to me to have less aspiration than in bow ties.
Interesting question, Petr. The way you express it seems to give the pronunciation of the phrase an objective existence beyond the individual realizations that will come with each individual speaker. You may be right for some speakers but not for others. My suspicion is that the aspiration might be different if the speaker is very consciously trying to maintain the individual words. If on the other hand the linking is fully subconscious, then the aspiration may be the same in both phrases. In any case, I don’t think it’s like the very clear aspiration difference like that you would find in the /p/ in pray and spray.