Both appear to be quite close as per Keys in Flora of Pakistan
, as below:
Keys are also available in Flora of China
, with phyllaries silvery gray to yellowish in Pseudognaphalium luteoalbum as per description in it
Other important aspects as per keys are:
Dwarf herbs, 10-40 cm tall; leaves 1-veined
Annual herbs; leaves spatulate or spatulate-oblong, apex obtusely rounded, base narrower.
Stems white lanate; leaf base decurrent, sometimes slightly amplexicaul; capitula 2-4 mm in diam.
Dwarf herbs, 10-40 cm tall, usually branched from base; leaves spatulate or spatulate-oblanceolate, not amplexicaul or auriculate, whitish tomentose on both surfaces; pappus connate at base. P. affine
Based on the above, I will have a relook at different posts in our database.