A hieroglyph corresponds to a linguistic element (word, affix, sound, whatever) whereas a pictogram corresponds to a concept or idea. Hieroglyphics is a form of writing; pictograms are not writing. Since ngutlh refers specifically to symbols used to represent language, mIllogh ngutlh makes sense for hieroglyph. A hieroglyphic writing system is a form of logography, that is, a system in which, basically, a character represents a word. So mIllogh ngutlh could be used for the broader logograph as well as hieroglyph. In the Toki Pona book, there's a table of hieroglyphs. In the introduction to this table, it seems the terms hieroglyph and logogram could be used interchangeably, so mIllogh ngutlh remains a good choice. But a distinction is made between these hieroglyphs/logograms (sitelen pona) and another set called sitelen sitelen in which logograms appear combined into single symbols rather than being displayed one after the other. Since the logograms used in the sitelen sitelen system are logograms (though not the same as the logograms in the sitelen pona system), mIllogh ngutlh can be used for these components.

All of this boils down to: Sure, mIllogh ngutlh is fine for hieroglyph as used in the book. (qep'a' 2022)