That's a myth and it doesn't count for current Apple Macbooks, internal components-wise, when it comes to capacitors, resistors and general power layout designs, they are pretty average. Just watch videos of Louis Rossman who repairs them on a daily basis, before the M1, Apple put the rail which powers the backlight of the display next to the power outlet rail which leads to many defects of the backlight lead being fried when it shorts through dust in the device.
The old macbooks endured very well but they had better board designs.
When it comes to Windows Laptops, there are many which come with 512 GB of storage and when they are upgraded, it's about 100 additionally.
Dell XPS Laptops I'd say are direct competitors which come with 512 Gigabytes standard.
It is just unacceptable to me for a "premium" brand to equip laptops with such few storage space.
To upgrade the base model from 8 to 16 gb and 500 gb storage nearly 500 Euro, that's just too much. The type of drive they are using and the ram are together 150 max. To add another 150 would be fine for the apple premium but they just take unnecessarily money based on how much people would border on finding it unacceptable.