Hello,
yes, for selectable text the image must go through text recognition (OCR). -convertToPDF only puts the image into a PDF.
OCR from the command line works with pdf24-Ocr.exe from the PDF24 program folder. It also accepts image files such as TIFF directly:
pdf24-Ocr.exe -outputFile "C:\Scans\output.pdf" -language eng "C:\Scans\input.tif"
Further options (several languages like eng+deu, -deskew, -autoRotatePages, ...) are described in the manual: https://creator.pdf24.org/manual/11/#101-command-line
Online you can do the same with OCR PDF: https://tools.pdf24.org/en/ocr-pdf