Minority followers of a religion do not broadcast pressure to other cities--they do receive/experience pressure from other cities.
Easiest case is when you are first, and extremely early, to found a religion (say, you're Ethiopia AND you popped a big faith ruin), and you've founded a couple of cities within 10 tiles of your capital, plus a couple of CSs are also in range.. Clearly the only source of pressure on the map will be your capital, experiencing 30 internal holy city pressure and broadcasting 6 pressure to your two other cities and the two CSs.
Initially, nothing shows up when you mouse-hover the various cities -- your 2 cities show your old pantheon and the CSs show nothing.
Roll forward X turns (still no one else has founded a religion) and you find that you have one follower in each of the CSs, each receiving 6 pressure (from your capital). In your two cities, one city (with 4 pop) shows 2 pantheon followers and 1 religion follower (receiving 6 pressure) and your other city (3 pop) shows 1 pantheon follower and 1 religion follower (6 pressure) and no longer shows the pantheon lightening bolt (neither your religion nor your pantheon is majority anymore). Importantly, your capital still just shows 30 internal pressure -- none of those minority followers in the CSs or your other cities is exerting any pressure on your capital. Minority followers in a city do not broadcast any pressure.
Roll forward Y turns, and you find that your two cities are now majority your religion (5 pop, with 3 followers, and 4 pop, with 2 followers). Because each of those cities is within 10 tiles of each other and the capital, each of those cities shows 12 pressure (6 from your capital and 6 from the other) and your capital is showing 42 pressure (30 internal holy city pressure and 12 pressure from your other 2 cities). When you look at the CSs, one of them (6 pop) is in range of all 3 of your cities, so it shows 18 pressure, but still only has 2 followers, so no majority religion. The other CS (also 6 pop) is only in range of your capital, so it still shows just 6 pressure and only has one follower.
Your nearest neighbor now founds his religion. His capital is not in range of any of your cities, but he is in range of the second CS (the one with 6 pressure and 1 follower). When he founds, you won't see any change in pressure at that CS, since it hasn't caused any conversions yet. To get a leg up, you send a missionary to that CS, convert 4 followers, and your religion is now in the majority, but still only shows 6 pressure (since only your capital is in range). If you look back at your capital, it will show 48 pressure - 30 internal holy city pressure plus 6 pressure each from your other 2 cities and 6 pressure from this newly converted CS.
Roll forward Z turns, and you see that CS (now 7 pop) still has 4 followers of your religion (still 6 pressure), but the other guy's religion now has 1 follower with 12 pressure! What gives? Obviously, he has 2 majority-religion cities in range of that CS -- his holy city and some other random city, maybe somewhere in the fog (causing you to mutter to yourself, "I gotta do a better job scouting").
Anyway, what's the point of this elaborate example? Focus on the interplay of that CS and your capital. If that lonely, minority follower of the other guy's religion could exert pressure on your capital, you would expect (if enough turns passed) that one follower would eventually show up in your capital with (presumably) 6 pressure. But no. It doesn't matter how many turns go by; as long as your religion is majority in a given city, including that specific CS, the only pressure that city (or CS) will broadcast is the pressure from your religion.
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