clarifying practical truths

A practical truth is not a direct substitute for a metaphysical truth and is different from a logical truth.
The universe began with the big bang =/= 'god is real'
                                                =/= '1+1=2'/'Eiffel Tower is in Paris, Paris is in France, the tower is in France'.
'Practical truths' are a part of a philosophy that sees 'truth' as a human concept.
Concepts do not demand realisation.
The concept of a unicorn is nothing but a fantasy, it makes the unicorn no less likely to exist.
Equally, the concept of 'truth' or 'beginning' do not demand realisation in the universe. Just because we see some things in the universe as behaving as we expect and deem labels of that behaviour as 'true' doesn't make them any more stable or real.
Just because we see 'things' as clusters of atoms forming and then ceasing to be the thing, doesn't mean that the universe inherantly has beginnings and endings. For example, a common question in physics is (or was), how did the universe begin? But the universe needn't have ever begun.

In this light, hopefully I have demonstrated that a practical truth is only used as a place holder for the sake of progress. We already use such things in science and every day life. All science, whether it is labelled as 'hypothesis', 'theory', or 'fact' is considered temporary, until a new theory which creates better results is found. When we act in life we do it based on our best knowledge. Getting to know a person we decide whether we want to see them again based on how they seem to behave. This is reasonable, rationale behaviour, but no one would say that we act based on an inherent truth about a person.

This philosophy doesn't deny that there is one reality. It is not idealistic, not believing that reality belongs to each individuals' experience. It is more realistic. It posits that reality is not knowable or unknowable. Because 'knowing' is a human concept that doesn't fit with what we know of the universe.