“Rav Chaim Kanievsky also made it clear that people should daven all tefillos with a Minyan during Bein Hazmanim.”
Of course. And obviously people should not sleep in and miss shacharis b’tzibur or be lazy and miss mincha/maariv just because they’re “off” from Yeshiva. But that doesn’t necessarily mean that it’s assur to do a productive activity (yes. vacation/relaxing/amusement can be productive) unless there are 3 minyanim a day in the vicinity.
Someone can be very committed to tefila b’tzibur and still make a cheshbon for the sake of his family to go on a trip where a mincha minyan (or any minyan) might not be possible. Either extreme (either not caring about minyan at all or never going anywhere without 3 minyanim a day) is well, extreme.