Indeed, the "cheese & soya milk debate" has been going on for years and there is no end in sight. I think it depends on some fundamental attitudes towards precepts & practices (sila-vata) of the individuals concerned rather than on what's actually stated in the texts, which is always subject to interpretation. Ajahn Brahm has written some Letters on Grey Areas in the Vinaya a long time ago, and they are still worth reading if you have access to them. Similarly, arguments about "what LP Chah allowed or not" are often dependent on the context in which that happened. He would say certain things to monks in Thailand and quite different things when he visited England, he was quite flexible in that way.
But on the subject of allowable tonics or medicines, there is also a noticeable difference between characters: the greed (lobha) characters will tend to be more generous and allow more, whereas the anger (dosa) characters will always favour the strictest interpretation possible and see any relaxation of such a standard as a threat to the Sasana
In Thai forest monasteries, there is actually a great variety of things which is considered allowable (in the Vinaya it mentions "leaves, roots, fruits, etc."). So sometimes monks will have a kind of Greek salad with olive oil and bits of cheese for the afternoon drink! During the previous economic crisis in Thailand, Wat Pah Pong officially "banned" cheese as a medicine, but this was because it was considered something expensive and luxurious (not like in the West), and a few years later everyone was happy eating it again. Soya milk is another such issue: in Thailand it is usually sold in the same way as cow's milk and people simply consider it to be in the "milk" category, therefore "food". However, in terms of Vinaya it could fall into one of two allowable categories (see Ajahn Thanissaro's book), it depends on how you define it.
As the Buddha puts it in the Maha-viyuha Sutta:
Those for whom precepts
say that purity's
a matter of self-restraint.
Undertaking a practice,
they devote themselves to it:
'Let's train just in this,
and then there would be purity.'
Those who say they are skilled
are [thus] led on to becoming.
But if one of them falls
from his precepts or practice,
having failed in his actions.
He hopes for, longs for, purity,
like a lost caravan leader
far from home.
But one who's abandoned
precepts & practices2
— all —
things that are blamable, blameless,3
not hoping for 'pure or impure,'4
would live in compassion & peace,
without taking up peace,5
on taboos, austerities,
or what's seen, heard, or sensed,
they speak of purity
through wandering further on
through becoming & not-,
their craving not gone
for becoming & not-.6
For one who aspires has longings
& trembling with regard to preconceptions.
But one who here
has no passing away & arising:
Why would he tremble?
For what would he long?"http://www.accesstoinsight.org/tipitaka ... .than.html