Once connected, the tool will identify the EMMC size. Do not format the entire flash. Use the "Partition Manager" to delete only the PRELOADER partition. Then, write the new preloader.bin extracted from your stock firmware.
The "new" landscape of MTK repair is dominated by tools that bypass traditional security measures to fix corrupted preloaders: MTKClient (Open Source) mtk preloader repair tool new
Dimensity & Helio G-series (G80, G85, G90, G99). This is an open-source Python tool that is updated weekly. It doesn't "repair" the preloader directly; it forces the CPU into BROM mode so you can rewrite the Preloader. Once connected, the tool will identify the EMMC size