I think that there might be crossed wires here. In the accounts, there will be an annual depreciation charge for the Tesla so that its value is reduced in the books over its working life. Let's work on the basis that the car cost £60k, and the depreciation charge is £10k per year. That's a fairly arbitrary figure based on the car been worth 20% of its origiinal cost after 5 years.
The depreciation is not tax deductible. In the year of purchase of the car, the depreciation is added back (the term for it being disallowed for tax) but the £60k cost will be deducted. That means that the taxable profits will be £50k lesss than the accounts profits.
In subsequent years, the £10 depreciation will still be added back, but there will be no further tax allowances for the car, so the taxable profits will be £10k
more than the accounts profits. This could be what the accountant means by his explanation. If so, I don't think that it's a very good (or even accurate) way of explainng things.
The reality of the situation is that you get a full allowance for the cost of the car when you buy it. When you sell it, the sale proceeds are brought in to tax, That means that you get tax relief on what the car has actually cost you in terms of depreciation over the period that you hold it. There is no question of paying back the initial tax saving. The only way that would happen is if you sold the car for the same as you paid for it, or for more. Not very likely.
This interpretation may or may not be correct. It's my best guess at deciphering the original comment, based on many years of explaning to clients that what the man down the pub said might not quite be what happens!