There is a big difference: spearfighters barracks can easily be removed before harvesting Alcatraz.
62 Iron age barracks will remain.
The player therefore deprives himself of other units with Alcatraz.
Well exactly that is happening in East-Nagach on international servers (62 barracks down, never go out), player doesn't care if he doesn't get any of units of his city age.
However, make no mistake, that barrack is built in 1h 20 min, and some similar time is required to train an archer. So even if you delete all of your Archery ranges before Traz collection, in a bit more than 6 hours you can again have 248 archers ready for exploiting. In next ~5 hrs 248 more, then again in ~5hrs 248 more...
I'm not saying there is no difference between spears and archers, I'm just saying both are an exploit, fixing one closes just one part of it.
To be frank, it's pretty apalling to me that you don't understand why it makes sense to exclude Bronze Age units from the AA map. How DOES it make sense that an age with no GvG representation, an age where a player can't even ACCESS the GvG map and also cannot contribute goods to the treasury (since they're unused) suddenly gets an opportunity to provide military units? Keep in mind that the only way this can be done at all is if a player is already past the age where they're featured, as a Bronze Age player, again, cannot even look at the map. This long-overdue exclusion is just confirmation that allowing Bronze Age units was an unintended oversight. They could have gone the other way and simply changed Spearfighters to train in an hour like the other Bronze units, but it's obvious that Inno's intent was to correct their mistake here. Took way too long, but these things usually do.
Until Bronze Age players are allowed to access the GvG map and they get a province to fight in, trying to defend including the troops in the AA province is simply laughable to me.
You really think spears were removed because bronze age players can't GvG anyway, and not because spearfighters were exploited on AA map by higher age players?
They can't change train time of spearfighters as they want to give players entering a world of FoE an opportunity to taste a game quickly before things slow down.
Removing spearfighters was not done because bronze age players can't enter GvG. Removing spearfighters was done solely as their build time was exploited by higher age players. And now archers are exploited because of their barrack size and train speed. Not a same, but a similar thing.
I posted two screenshots, one screenshot shows PME player producing archers, other screenshot shows a guild using archers, worth mentioning - that guild has no Iron age players, so try to guess if they were produced by higher age player or not.
So, that PME player has GvG ability as he advanced, and now he's using that ability to produce Iron Age Archers, by your reasoning "bronze age players can't enter GvG", why Inno stopped him from producing Spearfighters? Because that's an exploit.