I can explain. (sorry to but in)
"Indwelling" means it's in there. "FULL" means there's so much of it in there that there's (at that time) no room for anything else..like sin.
That is not the biblical understanding. You are correct that to be indwelt means that the Holy Spirit is IN every believer.
However, to be filled is a command, not an amount. The whole Holy Spirit is IN each believer. The issue is whether the believer is being filled or not.
So, let's examine the command to be filled:
Eph 5:18 - Do not get drunk on wine, which leads to debauchery. Instead, be filled with the Spirit,
So, we see a comparison here. Don't be "filled with wine" but instead be "filled with the Spirit".
What does wine to to people when consumed to excess? It changes them. It INFLUENCES them.
The same is true of the filling of the Holy Spirit. When good deeds are done when FILLED with the Spirit, the works are worthy of God's reward. But, otoh, when good deeds are done in the power of the flesh they are odious to God. Jer 64:6 - All of us have become like one who is unclean, and
all our righteous acts are like filthy rags; we all shrivel up like a leaf, and like the wind our sins sweep us away.
The red words in "filthy rags" actually refers to used menstrual rags in that verse.
Unbelievers, even atheists, are able to produce good deeds from their will power. And all that offends God.
Even believers can produce good deeds from their will power. And all that offends God.
ONLY when the believer is filled with the Spirit are the good deeds (fruit of the Spirit) acceptable to God and rewardable.
So, now the question: how is the believer filled with the Spirit?