Indeed. And AI search engines reveal the dimensions of whichever household product is used to compare ("What are the dimensions of a 170g can of Arrid deodorant?" ~5.5"). Of course, a tape measure is the most obvious -- if they don't use one, presume size and claim are unequal, but you may be nicely surprised.
Assume they're showing it to its best advantage, but remember we're not always at our very best. (Ignore those criticizing your interest. Providers post pics, and RM includes a filter, because legions of men (probably the vast majority) are interested. It's perfectly normal, and very common. Providers exaggerate because it's so common, just like real-life bottom-vers claim to be top on profiles -- it's what the market demands.)
You know what your own hard cock looks like in your own hand. It's a rough guide: if provider's hands don't close around his girth, or his cock barely peeks out the closed fist, you have an idea that he's super girthy or pretty short.
Beware dick pics taken from below -- favored because it looks bigger from that angle. Equally, ignore any dick pic without context (the disembodied cock, without hand or other comparand).