to be honest is realy easy spot mined coins.
You mine mostly in pools so then between you and pool is 1 adress.
mined > pool wallet > your wallet > exchange wallet.
Is easy to see such structure.
Most cases people mined some hot altcoin > exchange (mostly dead right now - since only "best in kind took those garbage" and sell ) > bitcoin.
So 80% people who mined in low scale in house will have such problem.
Most those altcoins︀ had to be sold as hot on very risky exchanges - is close to zero︁ prove that you had BTC not from direct mining.
There were also multi mining pools︂ so you were mining something but you were payed in most profitable coin at this︃ moment. Coins you had received was from regular exchange.
Clean situation is very rare like︄ mine BTC > pool > wallet.
Professionals who play that game they won't ask such︅ questions here.
There is close to 0 chance that someone who never mined can pretend︆ that he was mining in the past and prove it to people who know what︇ to check.
Most mulipools died / regular pools also / shity exchanges too , getting︈ evidence via mining is hard. Minig via staking/having supernode is easy since you use your︉ own node to mine. But this is likely like 5% of mining operations.
Summary :︊ is stupid to pretend that you were mining in 2012 but you have coins from︋ 2020/2021 XD... If someone realy mined BTC he will prove that easy. If someone like︌ me mined shitcoins to get BTC - case is almost lost in terms of 100%︍ transparency.
