[4bpp]

"as we see in figure 4" is simply incorrect, though; expressions such as "Figure 4" or "3rd Street" are treated as proper names and must be capitalised, as would the non-nominal "third" in "Dritte Straße" if any German-speaking city were to have American-style numbered streets.

[necovek]

Those two cases seem completely distinct: do you have a source for the claim that labeling stuff in documents with type and number makes those labels proper names?

For addresses, that's usually listen in a language grammar as a rule.