You should only draw conclusions after verifying facts. So what proof you provided us so that we can conclude towers don’t give XP? “Maybe” and assumptions don’t give us any proof, you just are guessing and make assumptions plus draw conclusions without a fair test.
There would be no logic in it that towers won’t give extra XP. Maybe XP is capped at a certain max, similar like max medals, but I don’t know this fact to be true or not. So your conclusion is that raiding a base without towers give same XP as a base with maxed towers, since you tell us towers won’t affect XP? Come on, you don’t believe that yourself.
A 9 month old video gives more proof than assumptions that you are making now based on just an inner feeling. Why would I assume that Flare changed the XP algorithm completely and left XP gained from towers out of the formula? You want to figure out whether XP is given by a tower or not, then a test can give us results that either support or bust your theory. Make fair test scenarios and exclude evertyhing else that can influence the results from the tests. So also no xp boost uber perk items please.
You should try the following scenario with another person. Remove all waves. Open your base and place no tower at all. Don’t summon anything and just use your sonic blast one single time and give up with two minutes remaining. Check XP points (I don’t think any will be rewarded unless time staying alive should give some XP). Then place a low tower just at the beginning. Destroy it with sonic blast and give up with two minutes left.You will see some XP, not much but still.
Go on and replace it with highest tower of that same type and raid and just destroy the tower with sonic blast and quit at exactly the same time. You will get more XP. Test it with other tower types, not just one. You can also try it with spikes, fences and barricades. Did you get different results sometimes or always the same? With different results you proved that XP depends on tower type, level of tower and boost (if there are boosts). Are the results the same (no xp), then you did proof your theory is correct, otherwhise you busted it.
You want to know if time influences XP? Just open your base and raid as fast as you can. Second time take it easy and slow, so that you need more time. Wanna test xp with waves. Just put in two waves with one troop. Wait near your base to destroy them and stop the time. Do the same with only one wave and stop at exactly the same time. That way you test situations and deliver proof.
This way of testing costs bread, some trophies and… some time, since you can only raid same person three times every hour. Trust me on this one, towers definitely give XP. Not much per tower, but they give XP and it depends on tower, level of that tower plus boosts. Only thing you can’t exclude out from this test is trophy amount. But you can exclude that by doing the same test twice in a row, since one player loses trophies, while the other one wins them. For example raid your highest tower twice. You will see same results.
You want to exclude hero level? Let another player do same, let him put a single tower in there without any waves and just a tower of same level. You should get exactly same results, since hero level has nothing to do with defense.