Work out what their motivation is; and get them to solve the problem for you
It seems to me that your PL is discriminating / bullying the English speaking employees.
FYI, If you/the team allow the non English coffee machine catchups to continue then it is possible you all could be liable (depending on local laws).
The PL may be behaving this way maliciously (trying to set up the foreigners for failure) or accidentally/unconsciously (e.g., because they lack the self awareness/ awareness of others; or lack of confidence in their own ability to use English)
"Don't attribute malice to what can be explained by incompetence"
That being said these kind of behaviors can be a result of some deeply held values/insecurities/past injustices. So be careful you don't push too hard lest you become a target; and don't try and win (that is the wrong motivation), and don't try to get everything uncovered sorted in one go, keep your cool and play the long game.
I would suggest doing two things:
'Get clarification' from management that "meetings" would be 'any time a group is together discussing something about the project/work' (try asking off line, but getting management to respond with a group communication).
Get them to solve the problem, using Observations and 'How questions'
A 'How question' is an open ended question that makes the person you are negotiating with, get out of their head and solve the problem for you.)
Make an observation at one of the 'coffee meetings'. Something like "It seems like <ABC> and <XYZ> are not going to be know that we discussed or be able to add their input"
Then follow up with a 'How question*' directed at the PL: "How will <ABC> and <XYZ> know what we talked about?" If the PL tries to turn it around and gets you to relay it to them, then keep asking follow up how questions "How will they be able to share their input to what we are discussing?"
Another observation & how question you may try is something like: "It seams like you (the PL) you don't seem comfortable taking meetings in English. How can we make having meetings in English more effective?"
Be careful to not corner your PL (no one likes that) and make sure you don't miss the key point ('having meetings in English') in the question. Re-ask the question (in a different way perhaps) if the PL tries an answer that drops the speaking in English part.
While making observations and asking How questions, watch for hints at what is really motivating your PL. Look for the thing which is really bothering them. Knowing that can help unlock what the real problem is. Keep an open mind it could be something surprising that you never would have thought of. It helps if you can pair up with someone so one of you is asking questions while the other is making observations/asking "How questions'.
Note also: That the example observations and how questions you using using the word meeting to describe the coffee catch ups, so you have subtly re-framed the sneaky loop hole back into what they are 'a meeting'.
Also very important, when doing this NEVER ask a question a how question that has a Yes or No answer; they must always be open ended. This can take some practice.
Credit where credit is due: Most of this is taken from the book: Never Split the Difference: Negotiating As If Your Life Depended On It., by Chris Voss
I highly recommend it, both for working effectively with colleagues, and your children Ha ha.