The BC547 and the MUN5211DW1 are completely different so that the schematic only look the same. The insertion of a pre biased dual transistor's abbreviated symbol into BC547 discussion on saturation is just confusing what could have been obvious became difficult by changing horses in midstream your.socks may get saturated.
https://www.rohm.com/electronics-basics/transistors/principles-digital-transistors
https://www.rohm.com/electronics-basics/transistors/principles-digital-transistors
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