I have noticed this for sometime and I can't seem to find an answer. Here are examples from Pro and the same raster as a published tile layer in AGOL. If you'll notice sometimes the legend is different too.
PRO
AGOL
PRO
AGOL
PRO
AGOL (NOTE: notice the legend appears different as well in this example)
PRO
AGOL (NOTE: notice the legend appears different as well in this example)
I'd appreciate if you'd let me know if this is normal or if maybe there is some secret to publishing tile layers. I've been working with Pro and AGOL for about three years and I've published countless tile layers but have not seen the questions asked. Maybe I'm to picky on how things look but I would think consistency from Pro to AGOL would be more seemless.