What is called "the string TRUE" by the OP is not a string (text) but the way Calc displays a numerical value in a cell set to the number format 'BOOLEAN' (listed as 'Boolean value'). It may be heavily misleading but is a fact that Calc displays TRUE for any value not equal to 0 an FALSE for the value 0 only in this case. [Let K3 be 0 to experience this.]

The second misleading behaviour of Calc in this context is that it automatically applies the number format BOOLEAN to a cell if it has the number format 'General' in advance and is recalculated to the result of a BOOLEAN function.

The third craziness I see in the fact that a cell once formatted this way will display every numeric result as 'BOOLEAN' even if the formula was edited to something without any relation to logic, "=PI()/8", eg.

And the fourth incredibility (or was it the zeroth) is that **an IF function is classified logical if the third or both the second and the third parameters are missing.** It will produce the logical result of the condition as its own result for the missing parameter. Very bad.

@johnlai2004 , for some reason, most likely because of a typo, **had first entered an incomplete IF expression**. Then he rectified that. This did not heal the consequences of silly smart automatisms.

You see?

@Edward is right in principle. We get rid of the insistent wrong format by choosing **another** numeric format but 'BOOLEAN'. 'BOOLEAN', however, is also a number format. I cannot but accept that.

By the way: Entering a numeric constant into the cell will also switch off the BOOLENA hysteria.